Importing dividends into excel from a fixed betting site....

I end up with a column of dividends. Next column contains the amount needed to bet to return $100.
My problem is that if there is a scratching, there is a blank cell and I am trying to divide by zero.

=if(isblank(a1),,100/a1)

This formula obviously leaves a value of zero if a1 is blank. I need it to return a blank cell for other formulas to work.

I formatted the number cells to 0;-0;;@ which apparantly hides the zero but the cell still has a value.

Can anybody tell me the correct formula...?
Thankyou everybody for your time...