Passing A Date Variable To Anaother Form

In form1 I've a command button to open form2.

Code in form1:

Private Sub button_Click()
On Error GoTo Err_button_Click

Dim stDocName As String
Dim stLinkCriteria As String

stDocName = "form2"
stLinkCriteria = button.Caption
DoCmd.OpenForm stDocName, , , stLinkCriteria

Exit_button_Click:
Exit Sub

Err_button_Click:
MsgBox Err.Description
Resume Exit_button_Click

End Sub

button.Caption contains a valid date value

In form2 I want to display the date in a label.

Code in form2:
Private Sub Form_Load()
Dim DatePassed As Date

DatePassed = CDate(Me.OpenArgs)
label.Caption = DatePassed
End Sub

On executing I get an error like "Invalid use of null value."

Who helps?