|I'll offer a suggestion below, but first a couple of posting tips.|
1 - Your subject line should be more than a request for help. It should be relevant to the question in your post. e.g. "Change Excel cell color" or something like that.
2 - Using words like "urgent" is not going get you an answer any quicker. People will respond to your post when they can, if they can, and aren't going to answer your post first just because you use "urgent" in the subject. You might even turn a few people off by implying that your question is more important than somebody else's.
3 - re: i want it to be done sheet wise instead of row wise.
I don't know what you mean by that. If the answer below doesn't help, please explain further.
Finally, look at the Help files on "Conditional Formatting".
Select the cells you want to format.
Pull down Condition 1 and choose "Formula is..."
Enter this in the field, modifying the cell references as required:
=IF($B1-$A1>2, TRUE, FALSE)
Click Format...Pattern tab..choose a color.
OK your way out.