FormCalc Help!

Hello,

I am a noob to LiveCycle designer and need help on a retirement contribution form.  I need the employee to select a payroll start date (which is a drop down list) and I have specified values so that each pay period equals a number (See January 9).  I have 3 options for the employees to enter for each contribution category (base, Age 50+ and 15 years of service).  The "Per Pay Check" is a field the employee needs to enter, but I need the annualized to pre-populate per the numbered payroll.  For example, if they choose to elect January 9th as their starting date, that means if they want to contribute $50 in the base section, it would be $50x24, because January 9 is the 24th payroll in a year.  This is the formcalc formula I am using in the first "Annualized" box and it's giving me an error.  Any help would be appreciate.

if paydate1 = 1 then

annual1 = base1*24