I have a worksheet with columns A through D. There are over 345000 rows in this worksheet. Columns C and D have data in every row. I have pasted a sample below. I want to fill the blank cells in columnc A and B with the values above the blank cells. I tried going to cell A3 and typing =A2, then highlighting columns A and B, then "Go To", and selected "Blanks". However, after a few seconds, a box popped up saying that the selection was too large. Is there another way I can do this?

A B C D
13-05 MASON,AMANDA L MAR 19,2013 14:33 TAMER,MARIA A
MAR 19,2013 12:23 TAMER,MARIA A
MAR 19,2013 13:38 TAMER,MARIA A
MAR 19,2013 13:42 TAMER,MARIA A
MAR 19,2013 14:30 TAMER,MARIA A
MAR 20,2013 11:29 TAMER,MARIA A
MAR 20,2013 11:43 TAMER,MARIA A
MAR 21,2013 14:08 TAMER,MARIA A
MAR 21,2013 14:10 TAMER,MARIA A
MAR 21,2013 14:11 TAMER,MARIA A
13-05 MASON,KATHERINE A MAR 13,2013 16:45 TAMER,MARIA A
MAR 18,2013 10:39 TAMER,MARIA A
MAR 18,2013 12:16 TAMER,MARIA A
MAR 20,2013 12:24 TAMER,MARIA A
MAR 20,2013 13:56 TAMER,MARIA A
MAR 21,2013 10:26 TAMER,MARIA A