Due to high volume of outbound calls you might be asked to alternate the outbound traffic by your termination provider.
Basically, what what you need to do here is: Having 2 destinations (Dst_A, Dst_B), check/set a variable in the AstDB. Then if the variable is 1, set it to 2 and route via Dst_A; otherwise, set it to 1 and route via Dst_B.
This code snippet might be what you are looking for:
Maybe in a future you might want to think in another approach to this task, but in the meantime this might come in handy.