In some cases, it is possible to use "will" in "if" sentences to imply 

**A) willingness**

>If you'll  just hold the door open for me a moment, I can take this table out to the kitchen.


**B) obstinate persistence**
>If you will keep all the windows shut, of course you'll get headaches

**C) if the "if" action is after the main action**, will (or an equivalent expression indicating the Future) is used in the if clause

>If aspirins will cure it, I'll  take a couple tonight. 


Please check [Wikipedia](http://en.wikipedia.org/wiki/Conditional_sentence#cite_note-lingua_org_uk_eqa-0) and [lingua.org](http://www.lingua.org.uk/eq&a.html) and [a page from Berkeley](http://www.icsi.berkeley.edu/~kay/bcg/lec07.html)