Using Dlookup in form - New to Access

I am trying to use dlookup in a form where I would like an unbound combo box
to fill-in with all the grants of an organization where the organization name
is entered in the form. The grant and organization fields reside in
tblGrantInformation and the form is bound to tblGrantPayment. When attempting
to follow the suggested Dlookup format (walking through it via the dlookup
function) I am not able to get any results - the unbound combo box is empty.
Any help is much appreciated!