[AccessD] OpenForm WHERE clause

I think this got lost in the shuffle the other day.

I'm setting a number of filters for a form using OpenForm. All of the
filters will use Is Null or Not Is Null for different fields, sometimes two
fields -- but always Is Null or Not Is Null. I've tried a number of
different syntax without success.

DoCmd.Openform formname, , WHERE clause

I've tried Is Null as a string, not as a string, I've used the IsNull
function in the form

"field = " & IsNull(field)

and even tried it all as a string... never could get it to work. I feel
really stupid -- this should be easy.

Susan H.