Gord,
Apologies for the delay in expressing my gratitude.
The following code that you kindly took the trouble to create and send to me works absolutely brilliantly!
Oh, I actually removed the Docmd.close... part at the end as I wanted to keep the form open for additional updations.
Many thanks again!
For anyone who is interested, the following code updates two fields in an underlying table to whatever selection you choose in these (combo boxes) for each and every record, criteria of the records being the selected autonumber field.
I probably haven't described the function of this code very well, but it is great, so please give it a go!
Private Sub CmdUpdate_Click()
On Error GoTo Err1
Dim SQL As String, Rs As Recordset, Db As Database
If IsNull(Me.Assignedto) Or Me.Assignedto = "" Then
MsgBox "Please enter or select someone to assign this to. ", vbInformation, "Required information..."
Me.Assignedto.SetFocus
Exit Sub
End If
If IsNull(Me.DateAssigned) Or Me.DateAssigned = "" Then
MsgBox "Please enter a date. ", vbInformation, "Required information..."
Me.DateAssigned.SetFocus
Exit Sub
End If
If MsgBox("You are about to update your records. Continue? ", vbYesNo + vbQuestion + vbDefaultButton1, _
"Record update confirmation..."

= vbNo Then
Exit Sub
End If
Set Db = CurrentDb()
SQL = "SELECT tblTempRef.RefNo FROM tblTempRef ORDER BY tblTempRef.RefNo "
Set Rs = Db.OpenRecordset(SQL, dbOpenDynaset)
If Rs.RecordCount = 0 Then
Rs.Close
MsgBox "No reference numbers found... ", vbInformation, "Required information..."
GoTo Exit1
End If
Do Until Rs.EOF
If IsNull(Rs!RefNo) Then GoTo StepOver
Db.Execute "UPDATE [Daily Metrics] SET DocumentsCurrentlyAssignedto = '" & Me.Assignedto & "', DateAssigned = #" & Me.DateAssigned & "# WHERE [Ref No]=" & Rs!RefNo
StepOver:
Rs.MoveNext
Loop
Rs.Close
Db.Execute "Delete tblTempRef.RefNo FROM tblTempRef"
Me.sbfmTempRef.Requery
MsgBox "All records updated successfully. ", vbInformation, "Success!"
DoCmd.Close acForm, Me.Name
Exit1:
Exit Sub
Err1:
MsgBox Err.Number & " " & Err.Description, vbInformation, "Update query error..."
Resume Exit1
End Sub