Kasper de Jonge explains how you can use a variable in the middle of an iterator:
As explained in the blog post the SUMX in this calculation will iterate over each row in the fact table which probably will have multiple currencies with different values for each date. The Min(FactExchangeRate[Factor]) will be evaluated for each currency and date and get the right value.
Now for those of you who have seen any of my sessions will ask why am I not using a variable as I always tell everyone to do so.
Click through for the answer and an example of where you can use a variable within an iterator.