Help with multiple IF statements & IF cell = blank

Hi everyone, I've used your site for so many useful tips & tricks but have been unable to figure one thing. For example, If a certain weekly pass has been returned (Y or N in F10) to auto figure the total based on d11. The original value is in cell A11

=IF(F11="Y",D11-15,IF(F11="N",D11)) Now this formula works great for me, but I do not want a return "False" I want it to also include the extra statement that if the cell is blank to equal the original A11 number.

I've tried incorporating IFEMPTY and IFBLANK but I keep getting the error saying to get assistance entering a function blah blah blah...

If the cell can either be Yes, No or blank, then:

=IF(F11="Y",D11-15,IF(F11="N",D11,A11))

else

=IF(F11="Y",D11-15,IF(F11="N",D11,IF(F11="",A11,"")))