...
If MsgBox(...) <> vbOK Then
    Exit Sub
Else
    Set rs = Me.RecordsetClone
 If rs.RecordCount = 0 Then
    MsgBox ...
    Exit Sub
 End If
    rs.MoveFirst
    Do Until rs.EOF
        Sum1 = Sum1 + rs.Fields(1)
        rs.MoveNext
    Loop

    rs.MoveFirst
    Sum2 = Round(Sum / Sum1, 3)
    Do Until rs.EOF
        rs.Edit
        rs.Fields(2) = rs.Fields(1) * Sum2
        rs.Fields(3) = Me.val                     ' текст валюты
        rs.Update
        rs.MoveNext
    Loop
End If