Adding a Condition to a Working Formula

[meppwc]

The formula below works correctly, but I want to add an additional condition. If cell A2 is blank, then do nothing, else, perform the working formula below.
I keep trying to add =IF(A2=''',''') to the formula below but no matter how I add it I am getting an error...............any ideas?

=IF(ISBLANK(L2),P2-O2,P2-L2)

 

[Special-K99]

=if(a2="","",if(isblank(l2),p2-o2,p2-l2))

 

[meppwc]

thanks so much...............I was leaving out the IF in front of (isblank)