Prevent duplicate Name&Surname combination in form

I have a a form like below with data source tblPatients.

I want to be warned of duplication when I add a new Surname & FirstNames combination.

When I enter a FirstNames, before update, I want the form to test whether an equal Surname & FirstNames already exists in tblPatients.

Will you please help me with the VBA.

Fritz PaulAsked:
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Rey Obrero (Capricorn1)Commented:
you can use a dcount() function in the before update event of Firstname

if dcount("*","tblPatients","[Surname]= '" & me.txtSurname & "' And [Firstnames] ='" & me.txtFirstNames & "'") >0 then
msgbox "name already exists"
end if

or to prevent error if surnames have special characters

if dcount("*","tblPatients","[Surname]= " & chr(34) & me.txtSurname & chr(34) & " And [Firstnames] ='" & me.txtFirstNames & "'") >0 then

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Neil RussellTechnical Development LeadCommented:
But of course there is no reason a all why the database can NOT have two patients with the same name.  There could easily be ten John Smiths in a patient records system.
Fritz PaulAuthor Commented:
Thanks Rey. Spot on.
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