macros for trigering events on focus loose

[nattynids]

I want to know, can we write a macro that does some acton when we loses our focus from one cell.
To be precise, i have column A which has some values. Now the moment the focus is shifted from any row of column value A, the value in that row of column A should get cpoied to same row of column B.
is it possible to do so or i have to write a macro that cpies the entire content of column A at once?

 

[nattynids]

hey one more help required if u can spare time. I want to format a cell in a way that it allows to enter only decimal values as it takes in time.
conditions:
1. only decimal values
2. only 2 digits after decmal
3. after decimal values allowed are 0-59 as it is minutes. but value before decimal could be of any range as it is accumulative time.

I tried doing this through format cells option in excel but not able to achieve.Can u suggest something.