Hello all

In Excell i need help from u all

i have three cells

1st cell= 1000
2nd cell=10
3rd cell= (1st cell -2nd cell)

now i get in 3rd cell as 990
if again i give 20 in 2nd cell
the third cell shouls display as 970 not 980

how to do this in excell
please help me

Reagrds
Bala