For it to work, you have to use a campaign structure as as far as I know, you can only store variables in a campaign, not between single missions. The command to do all the work for you,
saveVar.
I assume that you haven't played the OFP: Resistance campaign as there was a lot of variable saving (mainly weapons though) involved. I'm not sure how exactly things can be saved, probably by using saveVar at the end of a mission, or near the end and then using the variable in the next campaign mission(s). Should work, if not reply and I'll look deeper into it.