Blowing up background...
 

How can I do this, let me know please.

Well, the first thing that comes to mind would be a suitable amount of highly combustible material and at least one incendiary device to touch the whole thing off.

For something along the lines of what you are really asking for, I think you will need to be much more specific.

Are you trying to create software based visual explosive effects?

Are you looking for cap devices or props that simulate bomb explosions for an on-set shoot?

Are you trying to manipulate your in-cam settings for a zoom/scale focus effect?

Are you trying to manipulate the scale of an image layer in your NLE? If so, which NLE are you using?

-Jon

Oooh, I'm sorry buddy, not literally blowing something up... I mean something along the lines of a pair of hills in the background and my subject fairly close up and making the hills appear as though they are larger than they appear... Does this make sense?

zooming in compresses space...lengthening the DoF by closing the iris (bigger f-stop numbers) will keep it in focus for you.