I am having (I believe) a similar issue (See Default Value).
I have a form frmShippingRequestForm with a subform sfrmPackageDetails. My main form has a chkPersonalShipment, txtProjectNo, txtPersonalProjectNo, and txtContentDescription. If the chkPersonalShipment box is checked, then txtProjectNo is autofilled and disabled so the user can't change it. They must enter a personal project number. txtContentDescription is then automatically filled with "Bill to <PersonalProjectNo>" (where <PersonalProjectNo> is whatever value they enter in the txtPersonalProjectNo field). If the chkPersonalShipment box is unchecked, then the txtPersonalProjectNo field is disabled, and they must enter a department project number in txtProjectNo.
My subform is a datasheet, and can contain details for multiple packages in a single shipment. It has a Reference2 field. I need to set the default value to the value of txtContentDescription on the main form if the user checked the chkPersonalShipment box.
I've tried setting the default value with Me.sfrmPackageDetails.Form!Reference2.DefaultValue = Me.txtContentDescription (and several other variations), but it just displays "#Name?" in the field.
Any suggestions?