You need to add a function to validate the parameters. Go to the Report Properties under the Report menu and place this code to the Code Tab.
Public Function CheckDate(SDate as Date, EDate as Date) as Integer
Dim msg as Stringmsg = ""
If (SDate > EDate) Then
msg="Start Date should not be later than End Date"
If msg <> "" Then
MsgBox(msg, 16, "Parameter Validation Error")
Err.Raise(6,Report) 'Raise an overflow
Then go to the Report Parameters and Add named it XXX with the datatype as string. Checked the Hidden and Allow blank value ckeckboxes. In Available Values Read more about Validate Start date and End date parameter in SSRS[…]