So, using your example, I can't combine them into one statement?
=IIf([Mdid] = "ABC123", "\\Reportbackgrounds\ABCreport1.png", Null)
=IIf([Mdid] = "DEF123", "\\Reportbackgrounds\ABCreport2.png", Null)
=IIf([Mdid] = "GHI123", "\\Reportbackgrounds\ABCreport3.png", Null)