K5
=IF(AND(ISBLANK(H5),ISBLANK(J5)),"",IF(ISBLANK(H5),K4+(0-J5),IF(ISBLANK(J5),K4+(H5-0))))


I want K5 to be blank if h5 and j5 are blank.
If h5 = 0 , k5 should be k4+(0-j5)
If j5 = 0 , k5 should be k4+(h5-0)

H5 = =IF(ISBLANK(G5),"",F5*G5)
J5 = =IF(ISBLANK(I6),"",F6*I6)