Thanks for the input. I ended up getting it to work as follows in case someone else is looking for something similar:
nz(DLookUp("page_no","BL_File2","deliv_num=[Forms]![do a delivery]![deliv_num]")="2")
nz(DLookUp("page_no","BL_File2","deliv_num=[Forms]![do a delivery]![deliv_num]")="3")