DoCmd OpenForm Filter?????

[Bopsgtir]

Hi all im trying to open a form which will only show records where the CardNumber has not been entered, im using the below code but its openning the form and filtering ALL records???? any ideas.

Private Sub Command9_Click()

DoCmd.Close acForm, "FrmFuelCardManagement", acSavePrompt
DoCmd.OpenForm "FrmFuelCard", acNormal, , IsNull("[TblFuelCard]![CardNumber]"), acFormEdit, acWindowNormal


End Sub

 

[vbaInet]

"[CardNumber] Is Null"