User defined field that looks up a system table?

Question

I want to create a user defined field that looks up parts in the items table (i.e. OITM).
I know I can use a formatted search and that works, but I don't want users to be able to edit the field after the item has been looked up and pasted into the field.
In the user defined field menu, there doesn't seem to be a solution to this. The only solution I can think of is to create a user defined table and then move over the items, and then periodically have the table be updated from the master item table (OITM).
Thoughts?

Answer 1

Here is the stored procedure I wrote, but it doesn't seem to work:
IF @transaction_type IN ('A', 'U') AND @Object_type = '97'
BEGIN
IF NOT EXISTS (SELECT T0.ItemCode, T1.U_Part FROM [dbo].[OITM] T0, [dbo].[OOPR] T1
WHERE T0.ItemCode = T1.U_Part AND T1.DocEntry = @list_of_cols_val_tab_del)
    BEGIN
        SELECT @error = 1, @error_message = 'Testing'
    END
END
So basically, I have a UDF called U_Part in the Sales Opportunity form, which will have a formatted search to look up parts, but if a user changes the text to something else (which is possible because it's a basic text field), then this should look up what is in that UDF and check it against the Item Master and give an error if it doesn't exist. However it isn't doing anything.
Any ideas?
Edited by: Gary Rey on Jan 21, 2009 4:56 PM