Need help with a function

[Danchops]

I need help with a funtion in Excel XP. I would like to be able to enter in an x, y, and n in three separate cells, and then in a fourth cell write a function that would return x*y + (x*y)*y + ((x*y)*y)*y +(((x*y)*y)*y)*y...repeated n times.

Any help would be greatly appreciated.