If cell A1:A having text like (blank), then cell B1:B will be current date – 1 space 23:59 (example: 2/23/2013 23:39 ).
Please remember that always date & time format will be MM/DD/YYYY HH:MM
My actual data like following 
CELL A               CELL B
2/20/2013 6:57	2/20/2013 6:57
(blank)	        2/23/2013 11:33
2/20/2013 8:05	2/20/2013 8:05
I need to convert like below 
CELL A               CELL B
2/20/2013 6:57	2/20/2013 6:57
(blank)	        2/23/2013 23:59
2/20/2013 8:05	2/20/2013 8:05
I have tried something like below formula 
B1=IF(A1="(blank)",NOW()-1,A1)
B2=IF(A2="(blank)",NOW()-1,A2) ' here i want to keep current date-1 23:59
B3=IF(A3="(blank)",NOW()-1,A3)
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