Cells Of Object _Global Fails After Running A Sub.

I have a compilation of data on all employees ( named agents in here). On one sheet I will show graphs on diffrent figures for a specific agent. They choose which agent from a validation box in the cell 1,2 (range A2). When they have done that, I make a new list for the daterange and Cell 1,4 and Cell 1,6 (Range A4, Range A6) are validationboxes showing that list. The cells are empty to begin with.

When all validationboxes are filled, I do the graphs, and here comes the problem. After doing the graphs I get an errormessage on saying that "Method 'Cells' of object '_Global' failed" when it comes to the if-statement that has the Daterange-call in it. Ie: I dont get the errormessage when it DOESNT do the ShowCharts-sub, but after it has done that, I do get the errormessage.

Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Application.EnableEvents = False
Application. ScreenUpdating = False
'Cell 1,2 = Validation-box based on a list of agents
'Cell 1,4 = Startdate for the data to be picked for the graphs.
'Cell 1,6 = Enddate for the data to be picked for the graphs.
If Not (Cells(1, 2).Value = Empty And Cells(1, 4).Value = Empty And Cells(1, 6).Value = Empty) Then......................