Remove a entered item from a dependent dropdown list

[Elijah_Magrane]

Hi I have a app with that uses a dependent drop down list of raw materials to complete a bill of materials. However, the users find that it can be difficult to keep there place when selecting the raw materials.

Is there a way to remove an item from the list once it is selected ( I thought I saw a post detailing this before but I can find it)? The Raw materials table are ref to another table as well.