From what I can find, there doesn't seem to be a way to bind, say, a dagger to your offhand like you would a shield. Meaning, If I'm dual-wielding spells and have my mace bound to 1 and my dagger bound to 2, if I press 1 to equip my mace to the main hand and 2 to equip the dagger to my offhand, pressing 2 after 1 will simply equip the dagger in place of the mace in my main hand.

Is there a mod or something I can download to allow dual-wielding different weapons easier?

Thanks!

Extra hotkeys works http://skyrim.nexusmods.com/downloads/file.php?id=3865 but you need script dragon and it tends not to update very fast so I personally just go into the favorites menu and do it that way.