You can assign a macro to each scrollbar that will check if End Date is a valid date. Use the same macro for both scrollbars. In this code example, C3 has the start date, G3 has the end date. Whenever the end date is earlier than the start date, the macro will pop up a message and then set the end date equal to the start date.
Sub ScrollBar_Change() Dim ws As Worksheet Set ws = ActiveWorkbook.Worksheets("Sheet1") If ws.Range("G3") < ws.Range("C3") Then MsgBox "End date cannot be earlier than Start Date. Adjusting End date" ws.Range("G3") = ws.Range("C3") End If End Sub