In my opinion, this is a conditional statement for a future situation:
If you will do something, probably you are going to get or obtain another thing in reward.
If you will buy the groceries for your grandma, probably you are going to receive five dollars for that, or maybe she is going to allow you to spend the next week at her place.
In another hand, could be an answer, ie: I'll help you if you will go with me to the movies this Tuesday.;-)