Excel 2007 : Compounding Interest - Cumulative

is anyonne able to help me, I am trying to work out a formula to calculate compounded interest rates.

I have a table that is 24 columns wide (months).
1 row that will have amounts input in to the columns (these will be different amounts)

I want to have a row along the bottom that calulates the compounded interest at a fixed interest rate on the total amount that is in the first row.

i have mnaged to do this using a table but surely there is a formula for this as the table can become very troublesome if the input amounts change.

Ive added an image (attached) to hopefully make this a bit clearer.

Many thanks in advance if you can help you will be saving me days of work