So the computed column is ColA / ColB, what do you want the output to be.

If ColA is 10 and ColB is 0, do you want the computation to be 10 or 0

For 0

ISNULL(ColA / NULLIF(ColB, 0), 0)

For 10

ColA / ISNULL(NULLIF(ColB,0), 1)