How to go about retrieving data from data validation in cell to and listbox or textbox in userform

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I am creating a spreadsheet that holds a list of part numbers with their corresponding information. Right now I have it so that a textbox in userform entered like this (aaa-123,bbb-456,ccc-789) turns into a data validation in a cell within the same row as the part number. This is done because part numbers contain more than one quote number on several occasions. Once the quote numbers are within the data validation of a cell the user can select the proper quote number and other corresponding cells will populate with the quote information. This works perfect when entering a new part but I run in to trouble when updating an existing part. I was thinking maybe having a textbox that when you hit enter it populates a listbox that would then populate the data validation of the cell. But the contents of that cell would then have to be pulled back in to the listbox every time the user wanted to update the part with a new quote number. I could make it as simple as the entry in this form (aaa-123,bbb-456,ccc-789) populates a hidden cell and that cell creates the data validation and then when you update the (aaa-123,bbb-456,ccc-789) is pulled back into the userform and shown. This method would work but it wouldn't look good and scrolling through the quotes would be a pain. However, If someone could tell me how to create a multiline textbox that will return after a certain length is achieved that isn't based off the width of the cell that might work.