pls help me out

i have the data as below START DT(A1), END DT(B1), QUARTERLY COMMISSION DT.
(C1, D1.....)
A1 B1 C1 D1 E1
F1 G1
06.01.10 30.01.11 06.04.10 06.07.10 06.10.10
06.01.11 EXPIRD

HERE I WANT TO HAVE A FORMULA TO DRAG FROM C1 TILL I GET "expird" (WHEREIN I
SHOULD GET THE DATES FOR EVERY QUARTER FROM THE START DT. TILL THE EXPIRY
DT. AS ABOVE)

I HAVE USED THE BELOW FORMULA BUT THERE ARE ERRORS PLEASE CORRECT AND HELP ME
IF(DATE(YEAR(C2),MONTH(C2)+3,DAY(C2)<$B2),(DATE(YE AR(C2),MONTH(C2)+3,DAY(C2))))

THANKS IN ADVANCE