This is a visual basic 6.0 source code that inverts the case of the selected text. If the upper case text is selected then it will convert it into lower case text. Otherwise to upper case.

'*******************************************************
'*     MYCPLUS Sample Code - https://www.mycplus.com     *
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'*   This code is made available as a service to our   *
'*      visitors and is provided strictly for the      *
'*               purpose of illustration.              *
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Public Function InvertCase(ByVal Text As String) As Text
    Dim i As Integer
    Dim sBuff As String, sFinished As String

    'For every selected letter
    For i = 1 To Len(Text)
        sBuff = Mid$(Text, i, 1) '// Get letter
        Select Case Asc(sBuff)
            Case 65 To 90 '// If it is upper case
                sBuff = LCase(sBuff) '// make it lower
            Case 97 To 122 '// if it is lower case
                sBuff = UCase(sBuff) '// make it upper
        End Select
        sFinished = sFinished & sBuff '// Put that all in the buffer
    Next i
    InvertCase = sFinished
End Function