How can I add messagebox.show to show the answer in a messagebox.show?

Dim s As String
        Dim a, b, c As Long
        a = CLng(Val(TxtBoxInput.Text))
        s = TxtBoxInput.Text
        TxtBoxInput.Clear()
        For i = 1 To Len(s) Step 1
            b = CLng(Mid(s, i, 1))
            c = Len(s) - i
            b = CLng(Val(b) * (2 ^ c))
            TxtBoxInput.Text = CStr(Val(TxtBoxInput.Text) + b)


        Next i