How to convert text to value without blanks changing to zeroes

I figured out how to convert numbers formatted as text (eg. '10) into real numbers (eg. 10) so that I can do calculations on them, using the function:
but this also converts blank cells into zeroes.
Is there any way i can do this format conversion while leaving blank cells as blank (i.e. missing) numbers?
I guess i can test if the cell is blank by using the function ISBLANK(), but there doesn’t seem to be a BLANK or NULL function, and if i use




the result of converting a blank cell into a number results in zero (0).



Worked like a charm! Thanks for the quick reply.

Better than converting number string data through functions to numeric for calculations probably is to convert the data itself, see this FAQ.