Estimating - Assembly Formula with Operator?

Is it possible to use an operator within an assembly formula?  For example, I am building an assembly and for one part I would like to be able to use an "IF()Then()Else()" operator/statement.  However, when I try that and calculate it in my takeoff it sees the "Else" as a variable and, since it can't find it in my project values, it returns as 0.