Dealing with Duplicates ACROSS TWO tables

Hi all:

I have two tables that will be collecting a identification number of the clients in each table.  The tables are related but the ids, obviously, are unique.  Within the tables, I have put all the controls to ensure that there are no duplicates.  But how do I test "between" the two tables? 

For example, Client A's id is 1234 and she is entered in Table 1.
Client B's id is also 1234 and he is entered into Table 2.  

Which table the clients are entered into is based on other issues I don't need to describe here but I am positive I need the two tables, so making one table is not a solution.

So, how do I monitor when I have two clients across my two tables with the same ID of 1234 and that is not allowed?

Native solutions work best for me...not a coder but can learn.

Thanks!

Melissa

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Melissa Freel
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