If you are using a command button that would imply that you are always
starting and ending at the same place. If that is the case, you don't
need to "capture" the starting cell and can "hard code" the locations.
Assuming the button is on "Sheet1" and also on "Chart1" try...

Sub FlipFlopRevised()

If ActiveSheet.Name < "Chart1" Then
Sheets("Chart1").Activate
Else
Sheets("Sheet1").Activate
End If


End Sub