If you want to know the first cell after the freeze pane . Try this code-

Sub find_first_cell_after_freeze_pane()
If ActiveWindow.SplitRow = 0 And ActiveWindow.SplitColumn = 0 Then
MsgBox "No freeze Pane Found"
Exit Sub
Else
MsgBox Cells(ActiveWindow.SplitRow + 1, ActiveWindow.SplitColumn + 1).Address
End If
End Sub