Once again thanks for your help but i still get the same error when trying:

Dim task_start_date As String = txtStartDate.Text.ToString("MM/dd/yyyy") & " 00:00:00"

Dim task_end_date As String = txtEndDate.Text.ToString("MM/dd/yyyy") & " 00:00:00"

MsgBox(task_start_date & " " & task_end_date)

params(0) = New ReportParameter("User_Create", user_create, False)

params(2) = New ReportParameter("Task_End_Date", task_end_date, False)

Me.rptvUsersByCategory.LocalReport.SetParameters(params)

The error is occuring on the very first line with: Unable to cast object of type 'System.String' to type 'System.IFormatProvider'

Looking elsewhere on the net for the error i come up with other post with your solution suggested yet it does not work for me. I have tried stopping everthing and going in and out but still the error message !

Confused ![:'(]