Help with NOW() Formula to vary results in different cells

I am using a formula like this:
IN CELL B1 =IF(A1>0;NOW();0)
IN CELL B2 =IF(A2>0;NOW();0)
IN CELL B3 =IF(A3>0;NOW();0)
And so on...

And "A:A" has various calculations that return a number.

The problem I run into is, when ONE of the "B:B" cells returns a Date/Time result, they all return the same exact Date/Time result. But I'm trying to get different date/time results row by row. So, how do I get individual results?... if there is no other way besides VBA, then please provide a VBA for me.

Thanks!

ok so it seems that the NOW() function is not going to solve my needs. I need it to be more by individual cells, not for the whole worksheet.

Exactly what you said is what I need:

SHould B3 show the time when A3 was changed?

My answer: YES

---------- Post added at 02:26 PM ---------- Previous post was at 02:11 PM ----------

By the way... in my original formula example:
=IF(A1>0;NOW();0)

The "if false" result ";0)" is something I put because I didn't know better at the time, sorry. Rather it should be "C1")

Correction:
=IF(A1>0;NOW();C1)
=IF(A2>0;NOW();C2)
=IF(A3>0;NOW();C3)
and so forth...