Dim s As String = "AAABBBAABBBBAAABAAAABABBB"
        Dim lc As Char = s(0)
        Dim r As String = String.Empty
        Dim cc As Integer
        For Each c As Char In s
            If c = lc Then
                cc += 1
            Else
                r += cc.ToString() & "x" & lc & " "
                lc = c
                cc = 1
            End If
        Next
        r += cc.ToString() & "x" & lc
        Debug.WriteLine(r)

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov