Thank for your reply me ,but i have some problem.........
If the user region setting is Date format (DD/MM/YY) then , eg. (13/02/11)

but if the user region setting is Date format (MM/DD/YY) eg. (13/02/11), will error in isdate function, so how can i do ,
in isdate function convert the Maskedate.Text to do checking, base user region setting date format?

Dim dateEntered As DateTime
        DateTime.TryParse(Maskedate.Text, dateEntered)

 If IsDate(Maskedate.Text) = False Then
            MsgBox("Error available date !", 48, "Warning")
            Maskedate.Focus()
            check = False
            Exit Sub