how to sum value form Rows with gap

[imran khan]

i have thousand of data in Column A and Column B and i have simple formula of in Column C which is of minus a- b, but i have a question is that i write a formula in Column C (a1-b1) and then i copy formula and past in all the other upto for example (A100-b100) but what i want is that if i copy formula is only calculate where the value exists and where does not is shows blank.

A B C

1 15 12 =a1-b1

2

3 50 25

4

5 13 14 -1 -1 =

6 0 =

7 25 25 0 0

8

 

[shailyog]

use this formula in cell C1 and then copy to others cells:

=IF(AND(ISBLANK(A1),ISBLANK(B1)),"",A1-B1)