When the following code runs in my program, if the value of tpd_payments_lte.diff_pay = nothing (empty), the value of tpd_payments_lte.earned will evaluate to nothing. If the diff_pay amount = 0, it works fine. Is VFP 5.0 supposed to work like this?

REPLACE tpd_payments_lte.earned WITH (tpd_payments_lte.hours_worked * ;
tpd_payments_lte.hourly_rate) + tpd_payments_lte.diff_pay