Test for Field IS NULL on Form (1 Viewer)

[msp]

I am tring to test is a field is null on a form. If it is null I want to preform an action. However I am having problems checking to see if the form is null.

The code I have is

IF me.cbo_TrancheNo (isnull) then me.cbo_trancheNo.requery

This Obviously does not work I am hoping for a few pointers to help the test part.
#
Thanks in advance...

 

[Rich]

If IsNull(Me.etc) Then

 

[msp]

Thanks Rich

Toby

 

[ghudson]

Just incase the user keys data into the tested field and then clears the
value [because it will not longer be null but still empty]...

If IsNull(Me.etc) or Me.etc = "" Then