You might be better served by using data validation. Select the column or range of cells you will want to use to enter the part numbers in Sheet 1. Go to Data/Validation. In the Allow box, select list. Enter "=parts" (without the quotes) in the source box.

This will do two things. One, you will be able to click on a drop down arrow to select the part number. Two, it won't let you enter anything not on the original list.

If this method doesn't suit you, post back and we can figure out the formula for you.