always glad to help
I believe that the heal spell in combination with regeneration might help you out there. You see, the heal spell will cause the stumps of any severed limbs to in a way, want to grow back, but the heal spell is not capable of regrowing limbs. The regeneration spell, however, is, but cannot regrow limbs severed prior to the casting of the spell. In true munchkin rules lawyering style, you could have a two clerics, one casting heal while one casts regenerate. the heal spell would temporarily re-open the wound, and the regeneration spell would be in effect to take advantage of that. BING! New arm.
or what you could do should you have a powerful enough psion or psychic warrior in your party would be to have him remove the skin on the stub and 'suggest' to the cleric that the limb has been freshly severed. Considering that the effects of the spell depend on the mindset of the caster, a regeneration spell cast by a cleric under this effect would regrow the limb, no matter how old the wound.
and no, i'm not a munchkin, i just read 8-bit Theater too much.
Alternately, you could hire someone to cast a wish spell to restore your arm, if your party is incapable of doings so. If not, hey, you just found yourself a quest!
if your DM for some inconceiveable reason won't allow either, here's an idea to keep your char on her feet. have your DM pick up the Quintessential Dwarf, if he hasn't done so already. there are descriptions of prosthetic limbs that the dwarves could craft for you, effectively returning you to normal.