Using Data Validation to force a decimalized numeric entry

Data Validation is an excellent way to control data entry to meet a certain condition.

Suppose you want to insure that numbers entered in the yellow cells are OK for decimals, AND that only numeric increments of a quarter of a number are allowed. For example, the entry of 6.75 or 3.25 are allowed, but 4.35 or 1.62 are not allowed.

The following steps show how this can be done.