Is there a statue of limitations on how long my attorney has to send me a copy of my bill?

Question Details:

I hire my divorce attorney 4 years ago and paid a $2,500 retainer. About 2 1/2 years ago my divorce was finalized. I have been requesting a copy of my bill since then. I have called numerous times and have even sent numerous emails over the last 2 years but I have still not received a copy of my bill. I should add that I have a personal injury case that another firm has been handling (over 4 years). I don't know if she is waiting for my PI case to be resolved or what. I do not have any documentation stating how many hours she worked on my divorce case to even try and figure out a rough estimate of what the total cost would be. I am at my wits end and have run out of ideas on how to obtain a copy of my bill. Is there a statue of limitations on how long she can withhold my bill or is there something else I could do to get the information I need? Important Notice