Updating records using the results of another Recordset

Morning All,

I hope someone can help me here...
I am trying to fill in the blanks within the records of a table using information already in that table.
i.e: I have five records with the same 'premise code' but only on has 'Tier' information - I want to be able to put this information in all 5.

I thought I had it with this code but when I run it Access just shuts down on me...program not responding.

Could someone have a look and maybe VET my code and tell what what simple thing I am missing.

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Private Sub Tier_Click()

Dim db As DAO.Database
Dim rs As DAO.Recordset
Dim strSQL As String
Dim strSQL2 As String

strSQL = "SELECT DISTINCT [Premise Code], Tier "
strSQL = strSQL & "FROM [Combined List] "
strSQL = strSQL & "WHERE Tier Is Not Null;"

Set db = CurrentDb
Set rs = db.OpenRecordset(strSQL)

Do Until rs.EOF
strSQL2 = "UPDATE [Combined List] SET Tier='"
strSQL2 = strSQL2 & rs!Tier & "' WHERE [Premise Code]='"
strSQL2 = strSQL2 & rs![Premise Code] & "';"
db.Execute strSQL2
rs.MoveNext
Loop

End Sub
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Any help would be much appreciated