Private Function TitleCaseSplit(str As String, Optional delim As String = " ", Optional upper_case_indicator As String = "") As String
    Dim chr As String, out As String
    Dim state As String
    Dim i As Integer
    Dim is_upper As Boolean
    chr = Mid(str, 1, 1)
    out = chr
    state = "first character"
    For i = 2 To Len(str)
        chr = Mid(str, i, 1)
        is_upper = StrComp(chr, LCase(chr), vbBinaryCompare)
        Select Case state
            Case "first character"
                If is_upper Then
                    state = "upper-case word"
                Else
                    state = "title-case word"
                End If
                out = out & chr
            Case "title-case word"
                If is_upper Then
                    state = "first character"
                    out = out & delim & chr
                Else
                    out = out & chr
                End If
            Case "upper-case word"
                If is_upper Then
                    out = Left(out, Len(out) - 1) & upper_case_indicator & Right(out, 1) & chr
                Else
                    state = "title-case word"
                    out = Left(out, Len(out) - 1) & delim & Right(out, 1) & chr
                End If
        End Select
    Next
    TitleCaseSplit = out
End Function

Private Function TitleCaseSplit(str As String, Optional delim As String = " ", Optional upper_case_indicator As String = "") As String
    Dim chr As String, out As String
    Dim state As String
    Dim i As Integer
    Dim is_upper As Boolean
    chr = Mid(str, 1, 1)
    out = chr
    state = "first character"
    For i = 2 To Len(str)
        chr = Mid(str, i, 1)
        is_upper = StrComp(chr, LCase(chr), vbinarycompare)
        Select Case state
            Case "first character"
                If is_upper Then
                    state = "upper-case word"
                Else
                    state = "title-case word"
                End If
                out = out & chr
            Case "title-case word"
                If is_upper Then
                    state = "first character"
                    out = out & delim & chr
                Else
                    out = out & chr
                End If
            Case "upper-case word"
                If is_upper Then
                    out = Left(out, Len(out) - 1) & upper_case_indicator & Right(out, 1) & chr
                Else
                    state = "title-case word"
                    out = Left(out, Len(out) - 1) & delim & Right(out, 1) & chr
                End If
        End Select
    Next
    TitleCaseSplit = out
End Function

Private Function TitleCaseSplit(str As String, delim As String) As String
    Dim chr As String, out As String
    Dim state As String
    Dim i As Integer
    Dim is_upper As Boolean
    chr = Mid(str, 1, 1)
    out = chr
    state = "first character"
    For i = 2 To Len(str)
        chr = Mid(str, i, 1)
        is_upper = StrComp(chr, LCase(chr), vbinarycompare)
        Select Case state
            Case "first character"
                If is_upper Then
                    state = "upper-case word"
                Else
                    state = "title-case word"
                End If
                out = out & chr
            Case "title-case word"
                If is_upper Then
                    state = "first character"
                    out = out & delim
                End If
                out = out & chr
            Case "upper-case word"
                If Not is_upper Then
                    out = Left(out, Len(out) - 1) & delim & Right(out, 1)
                    state = "title-case word"
                End If
                out = out & chr
        End Select
    Next
    TitleCaseSplit = out
End Function

Private Function TitleCaseSplit(str As String, delim As String) As String
    Dim chr As String, out As String
    Dim state As String
    Dim i As Integer
    Dim is_upper As Boolean
    chr = Mid(str, 1, 1)
    out = chr
    state = "first character"
    For i = 2 To Len(str)
        chr = Mid(str, i, 1)
        is_upper = StrComp(chr, LCase(chr), vbinarycompare)
        Select Case state
            Case "first character"
                If is_upper Then
                    state = "upper-case word"
                Else
                    state = "title-case word"
                End If
                out = out & chr
            Case "title-case word"
                If is_upper Then
                    state = "first character"
                    out = out & delim
                End If
                out = out & chr
            Case "upper-case word"
                If Not is_upper Then
                    out = Left(out, Len(out) - 1) & delim & Right(out, 1)
                    state = "title-case word"
                End If
                out = out & chr
        End Select
    Next
    TitleCaseSplit = out 'Mid(out, Len(delim))
End Function

Using VBA (Visual Basic for Applications) in MS Access, I needed to convert TitleCase to lower\_case, but did not have the regex enqine that's available in VB Script.  This solution,  based on a simple state machine model, splits the words in the string (converting to lower-case is trivial after that).  It treats a block of upper-case letters as a single word, but the last letter of that block is the first letter of the next word; e.g., "VBAIsLame" becomes "VBA Is Lame".   Because of this behaviour, if you subsequently convert to lower-case, you cannot reliably convert back to the original (all-upper-case words are indistinguishable from title-case words).  To resolve this potential ambiguity, you can supply an "upper\_case\_indicator" that will be inserted before each capital letter that isn't the start of a word.  So `TitleCaseSplit("VBAIsLame", "_", "-")` returns "V-B-A\_Is\_Lame".

Splitting the words in a  TitleCase string without using regular expressions (for VBA)

Visual Basic