Insert descriptive text in another row when specific number is entered

Using a customized form at work...I need to insert about 3 lines of a text decription when the number for that text decription is entered in the line above.

Example...a parts order form. When I enter part #1234 in the cell, a part description of about 2-3 lines is inserted to the line below the entered part number.

And once I get the cell references figured out, where am I typing or keeping the actual part description texts that are being referenced and inserted into the specific cells?

Thanks for any help!!!