If statement involving numbers and text

Hey,

I am trying to make an If statement that will look determine if a cell is a number or text, if it is a number than display that number times a constant, if text than display a different cell. Here's what I've got so far:

=IF(F12>0,F12*85,L12)

The true part is working, but the false returns a #value! error. I'm thinking I need to nest another if statement but don't know how to tell excel to differentiate between numbers and text. Note: The text in the cells are all different, so I think I'm looking for something that indicates generic text.