Ignore Text for Formula

I've got a cell that will either produce a numeric vakue as the answer or subject to an If Statement will produce nothing ie "". I'm using "" rather than 0 as I don't want it to be visable unless it's a number.

My problem is that I want to use the answer from this cell in further calcs. The calc is just adding two cells ... but if the answer to the cell has text then just ignore it and produce the value in the first cell.

Eg. A1 + A2 = X
Where A2 = Text then = A1

Thanks Dave ... appreciated