Help!! Joining vidoes so thaey overlap

[chetan121212]

i need to join two equal length videos so they overlap each other. for example im filming one room and there is one chair for 2 30 second clips. i put an object on the left side of the chair and in the other video i put it on the right, i want the final video to show that two people put two objects on that chair in the at the same time for the same 30 seconds. please this is very important i need this answered asap. i have adobe premiere/ after affects 5 encase that helps.

[edDV]

Read up on compositing.