Vlookup affecting an IF formula

Hi

I am using the following formula in IA7 to work out total hours between the end of one shift and the start of another:

=IF(ISBLANK(HW7),"",IF(IB7="","",MOD(IB7-HX7,1)))

This was working fine until I entered a Vlookup formula into HW7 which now enters 00.00 into the cell and therefore throws off the above formula -

Basically if HW7 = 00.00, then I want IA7 to remain blank, as soon as other values are entered, I need the calculation to work - any suggestion on how I can do this?

Thanks in Advance

Hi

Thank You both for your quick replies - Richard I did try your suggested formula intially but Excel came back with an error and a solution involving a * between the two statements - However I must have madee an entry mistake as it works great now!! (there's only so many brackets and "" you can look at before they all blur into one)

Thank you both again!