How to restrict users from putting decimal values in a System provided number Field.

Hi,

The issue is: in the Special Pricing Product there is a System Provided Field called: Quantity. This is a Number Field, which accepts decimals upto 2 Places.

Ideally Quantity of a Product cannot be in decimals, and it has to be in whole numbers. Since it is a system-defined field, we retained the field and decided against a Custom Integer Field.

Now, as natural the Quantity field in Special Pricing Product accepts a decimal value like: 10.05 or 11.29 .. like this.

I want to know is there an expression (sample Expression) by which I can put in a field validation that will restrict users to key in a decimal value in the Quantity field.