Prevent Duplicate entries in multiple column from VBA Userform

Dear Team,

I have a vba userform which enters data into multiple sheets. For two comboboxes, there can be "X" combinations like as follows:

Column B Column C
John Red
John Black
Michael Red
Michael Black

I want to prevent duplicate entries into columns. Currently I am using following code but it doesn't allow me to add multiple combinations. e.g. It won't allow me to add "Michael Red" if I have added "John Red" earlier in sheet.

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Please help for this query.

Would it be possible to have another column, maybe hidden, with a formula that combined the B and C values, and then compare your entries with that? So your formula in G2 would be

Formula:

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and your code would be

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