Access- -Prevent New Record

I have on my form a button which now copies information and will copy it to a new record when pressed. I would like this to happen unless the date is not filled out. If the date is not filled out, I would like a msgbox to appear letting the user know that it is not complete, and a new record would not be created. The problem I am running into is my statement I believe. I keep getting an invalid use of null error statement. I am testing the date field and if it is empty I want the message to appear. Is this a possibility? Thanks for any help.

Something like this :

Textbox1.SetFocus
x = Textbox1.Text
If x = "" Then
MsgBox ("Please enter a date.")
End
End If