In reply to clemenzasauce:
Best way is with triggers. You could store the information using Integer variables. Every time a unit is created, or if you have set units already on the field, simply modify your variable in a global variable. You should use an array so that it corresponds to every player. You could have simple triggers that add or subtract to your global variable which would act as a counter to how many units you have.
A lot of board games do this sort of thing, such as Axis And Allies. They use red chips to basically act as 5 units, since the board game cannot accommodate dozens of units chips make it an easy way to have more units then they have plastic pieces for.