Where on the elbow do you get the pain?

If it is on a bony prominence on the outer aspect I would suspect Wikipedia reference-linkTennis Elbow. This is caused by repetative gripping actions, but also by the use of vibrating tools at work.

To test for this, put your arm out straight in front of you (palm side down) and try and pull the wrist up (into extension) using the resistance of the other hand. Does this cause you pain? You can also resist extension of the middle finger. Again, does it cause pain?