bods: date comparison is going wrong

Hi all,

i have a requirement to do a calculation on a date if the date is not blank.

if the date is blank, then do nothing.

i am trying to execute the below script in a transformation column:

ifthenelse('2014.12.15 04:15:00.000000000' <> $b , <calculations-here>, $b);

where $b is of type datetime and not assigned anything , means it is blank.

the output is supposed to be the calculations in the if part,

but the actual output that i am getting is blank.

Please provide your suggestions.