Just brilliant Kostis. Thanks so much for solving my dilemma.
regards from Australia
Warren

"vezerid" wrote:

I am assuming that the headings for the months are the first day of the
month. Otherwise we will need a somewhat more elaborate formula. I am
also assuming that increase starts counting on the day quoted. Then,
with the month-first-days being in cells J1:J12 and increase date being
in B2, you can use the following formula:

=(50000+IF(MONTH(J1)<MONTH($B$2),0,IF(MONTH(J1)MO NTH($B$2),3000,3000*(DATE(YEAR($B$2),MONTH($B$2)+1 ,1)-$B$2)/(DATE(YEAR($B$2),MONTH($B$2)+1,1)-DATE(YEAR($B$2),MONTH($B$2),1)))))/12

HTH
Kostis Vezerides