The ABS Function
Returns a value of the same type that is passed to it specifying the absolute value of a number.
Syntax
Abs(number)
The required number argument can be any valid numeric expression. If number contains Null, Null is returned; if it is an uninitialized variable, zero is returned.
Remarks
The absolute value of a number is its unsigned magnitude. For example, ABS(-1) and ABS(1) both return 1.