VB Forms and giving an error when a combo of 2 fields already exist in the data

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Hi all,

I have a form in VB with BO that have parent/child relationships. I have a table called 'Input' that holds the data when user clicks submit. In this table, I want an error message to pop up if a combination of tag number (text field from input table) and supplier name(this belongs to a table named 'Supplier' and it is the parent of the table 'Input') already exists in the 'Input' table.

I thought making both fields unique in the 'Input' table would solve this issue, but it treats them separately instead of as a combination.