Incubus3,
I don't know whether or not you are still trying to figure out this question, but I offer my brief input. I use 123 Release 5 and 123 Millenium, but they are very similar in nature. I used the following formulas exactly as written:
@IF(F4=3,1.73,1)
+L4*I4
Note: I used commas rather than semi-colons and they work. I realize that the help files tell you to use semi-colons, but when I placed them in the formula the program itself changed them to commas. Go figure.
Provided that there is in fact something in F4, a value of either 1.73 or 1 will be returned in cell L4. Provided there is actually a number in cell I4 a value will be returned in cell M4.
You may face a problem with the appearance of numbers in cells that are actually labels so perform some calculations with them to see if in fact things are adding, subtracting, multiplying and/or dividing. You shouldn't get an error if all four of the cells involved here are in fact numerical in nature.
Hope this helps.