Developers not turning over association funds

The developers our building (a 5 unit gut renovation) never turned over the dues collected or an accounting of what was spent, even after they now longer owned any of the units. We decided to start collecting dues ourselves, set up a bank account and elected a treasurer. We have since retained a lawyer and they still say they only owe us $2000. We believe they owe us closer to $5k (which is a lot for a brand new association). The lawyer said they aren't required to give us proof of payment or bank statements. We believe they were commingling funds (owners made dues checks out to the individual, not the association). Aren't we entitled to see that they've truly paid a bill, not just produce a bill? When the last unit was sold, the owner was given a condo budge (which those of us who already purchased never saw) that indicated % ownership and dues per unit. Now that they need to pay us for the unsold units after the first units were sold, they are trying to use lower, different figures for those units. Help! We are so frustrated. I won't even get into construction issues...