@Tom Collins's solution is great, but if you wanted to use just Excel and no VBA, you can use an EVALUATE function in Excel, but not in the way you would expect. It's not a regular worksheet function.
You'll need two helper columns, one to contain the concatenated formula, and one to display the final result.
In D1 you'd have
This will compress the separate formula pieces into one cell. You then need a range name to convert it into an evaluated format.
On Excel 2007 / 2010, go the Formulas tab and Define Name. In name you can use Answer, and in Refers To enter the formula
Then in E1, you can enter
and drag down.