True/False Statements in Access

I need to make a string of numbers (ssn) turn a different color if they appear more than once in access.

Can anyone assist me with my statement.

 

If you're displaying the SSNs on a form, use the Conditional Formating to test a function which return True or False, based on the existence of duplicates. Change the back color of the control using the menu Format|Confitional Formatting.

The menu Format|Conditional Formatting expression is fCheck4Duplicates[SSN], being either True or False. Set the color at your discretion.

The class module function is a DAO/ADO instruction sequence checking for counting duplicate SSNs, e.g.

public function fCheck4Duplicates(sSSN as string) as boolean
dim db as dao.database
dim rs as dao.record
dim strSQL as string
fChech4Duplicates=False
set db=currentdb
'returns count of SSN if gt 1
strSQL= "SELECT SSN, Count(SSN) AS NumberOfSSN FROM YourTableName GROUP BY SSN HAVING SSN =" & CHR(34) & sSSN & chr(34) & " AND NumberOfSSN >" & 1
set rs=db.openrecordset(strSQL,dbopensnapshot)
'no records
if rs.eof and rs.bof then goto Exit_Exit
'a record exists, count has to be > 1
fChech4Duplicates=True
rs.close
db.close
set rs=nothing
set db=nothing
end function

I'm not guaranteeing that this is going to be extremely fast because each row has to be checked. Furthermore, you may experience some screen flicker with a large number of rows while the calculations are being permormed. Mousing over the form stops the screen flicker.