Synopsis
An error in some mathematical expression/assignment, for example attempting to add a numeric value to a variable whose value is not numeric, as so:
my_var = "hello" sum = my_var + 30Cause
Cure
Do not put your variable name in quotes when used in a mathematical expression.
Cause
You used a variable that was never assigned any value. Therefore, its default value is its name in capital letters. A variable's name is not a numeric value.
Cure
Make sure that you assign a numeric value to the variable before using it in some mathematical expression. You can trap the NOVALUE condition to catch errors of this nature.