Drag and Drop; Variables

I have a drag and drop exercise with 23 items and 5 drop targets. Of the 23 items,  19 have “correct” drop targets and 8 of the 19 have multiple correct drop targets.  I have all of this functioning correctly. The client has decided they wants 3 correct items per each of the drop target (total 15). Once the learner achieves this, they are to be prompted to go back to the Main Menu.

Can I assign a certain number of items that must be dropped on each target and then once the learner achieves 3 per target, prompt the learner to return to the Main Men?

If not, the client would be satisfied for 15 correct drops – regardless if they are 3 per target. Would I create a “counter” variable so that each time an item is dropped correctly it increases the counter variable by 1? Once the counter variable reaches 15 display the prompt?

Any suggestions on the best way to accomplish this?

Thanks in advance!

Sherry