Hi Raj
The answer is yes.
You can use the event background processing multiple times. And the if else condition you provided as example will work.
Where to use Background processing-
To optimize your application performance you can use this event to load datasources inorder to decrease the startup time.
If you wish to do a repetitive operation instead of using background processing option use a button and call its Onclick event wherever needed.
If you are in DS 1.4 you can also use global script functions to perform various operations.
Just to clear your doubt ,this has nothing to do with parallel processing ,Read here for more information parallel processing,
Thanks