Formulas interfering with check for text

I want to check for text in a cell. My formula is

=IF(ISTEXT(I3),"yes","No")

However, the cells I want to check are populated with formulas, similar to

=IF(A3="Bob", G3,"")

So, I only want to do something with the ones that actually have a value (but it's a name, so text) populating my cells. How do I get my ISTEXT formula to do what I want?

Thanks in advance,
John