title: Run time error '3164': 'Field cannot be updated' - Access VBA issue
body: <p>I'm having an issue with a piece of VBA I've written for Access. I have a table with a concatenation field 'Concat' (string field) and field called 'Age' (integer field with numerical values). </p>
  
  <p>There are another 61 fields (named '0','1','2'...'60' respectively) where the code needs to work though: I want the code to loop through and, per record entry - for the VBA to Dlookup using the Concat + age fields to another table (called: tbl_Final_Probabilities) and pull back a probability and populate each of these 61 fields with the correct probability. These fields are set up at a numerical field, data type as Single.</p>
  
  <p>The code pulls the correct probability but when I try to update the record for that field at the code line: "rs.Fields(a) = b" (also highlighted in code), I get the error message: "Run time error '3164': 'Field cannot be updated'".</p>
  
  <p>All help welcome on how I need to correct this please, the code used is below.</p>
  
  <p>Punch and pie.</p>
  
  <h2>Code:</h2>
  
  <pre><code>Dim rs As DAO.Recordset
  Dim a As Integer
  Dim b As Single
  Dim lookup As String
  
  Set rs = CurrentDb.OpenRecordset("SELECT * FROM tbl_Circuit_plus_prob")
  
  For a = 0 To 60
  
      If Not (rs.EOF And rs.BOF) Then
          rs.MoveFirst
  
              Do Until rs.EOF = True
  
              rs.Edit
  
              lookup = rs!Concat &amp; (rs!age + a)
  
              b = DLookup("Prob_Date", "tbl_Final_Probabilities", "Concat2 = '" &amp; lookup &amp; "'")
  
              rs.Fields(a) = b  '- CODE BREAKS DOWN HERE
  
              rs.Update
  
              rs.MoveNext
  
              Loop
  
      End If
  
  Next a
  
  rs.Close
  Set rs = Nothing
  </code></pre>
  
  <p>Thanks in advance for any and all help.</p>