To assign a conditional value, use the function.

To assign a conditional value, use the IFF function.  It is an abbreviation for  Immediate If.  It is a function on spreadsheets that returns the second or third parameter based on the evaluation of the first parameter.  You use IIf to determine if another expression is true or false. If the expression is true, 
IIf returns one value; if it is false, IIf returns another.