But ... why?
You're essentially doing double the work and costing yourself materials.
Here are the scenarios:
1) You use 100 crowbars (200 points of enchanting) to enchant some green/blue items and get back 150 points of enchanting. You then use those 150 points to enchant the actual gear you want.
2) You use 100 crowbars (200 points) to enchant the gear you want.
You're doing double the work for no reason. It's not actually saving you a step since you have to use those crowbars in both 1 and 2.