Option Explicit
 
Private Sub Form_Load()
Text1.Text = "This is a test. This is only a test."
End Sub
 
Private Sub Command1_Click()
Randomize
Dim ForLoopCounter As Integer, TextLength As Integer, TempInt As Integer
TextLength = Len(Text1.Text)
For ForLoopCounter = 1 To TextLength
  If Mid(Text1.Text, ForLoopCounter, 1) <> " " Then
    TempInt = (Rnd * 1) + 1
    If TempInt > 1 Then
      ChangeCase ForLoopCounter, True, TextLength
    Else
      ChangeCase ForLoopCounter, False, TextLength
    End If
  End If
Next ForLoopCounter
End Sub
 
Private Sub ChangeCase(Position As Integer, UpperCase As Boolean, StringLength As Integer)
If Position = 1 Then
  If UpperCase = True Then
    Text1.Text = UCase(Left(Text1.Text, 1)) & Mid(Text1.Text, 2)
  Else
    Text1.Text = LCase(Left(Text1.Text, 1)) & Mid(Text1.Text, 2)
  End If
ElseIf Position = StringLength Then
  If UpperCase = True Then
    Text1.Text = Left(Text1.Text, Len(Text1.Text) - 1) & UCase(Right(Text1.Text, 1))
  Else
    Text1.Text = Left(Text1.Text, Len(Text1.Text) - 1) & LCase(Right(Text1.Text, 1))
  End If
Else
  If UpperCase = True Then
    Text1.Text = Left(Text1.Text, (Position - 1)) & UCase(Mid(Text1.Text, Position, 1)) & Mid(Text1.Text, (Position + 1))
  Else
    Text1.Text = Left(Text1.Text, (Position - 1)) & LCase(Mid(Text1.Text, Position, 1)) & Mid(Text1.Text, (Position + 1))
  End If
End If
End Sub