Private Sub Кнопка_Click()
Dim strSQL As String
Dim cmd As ADODB.Command
Dim retval
Dim intMonth As Integer
retval = MsgBox("Следующий месяц уже наступил?", vbYesNoCancel)
    If retval = vbOK Then
        intMonth = Month(Now)
    ElseIf retval = vbNo Then
        intMonth = Month(Now) +  1 
    Else
      Exit Sub
    End If

Set cmd = New ADODB.Command
strSQL = "INSERT INTO tbl ( IdSotrud, uMonth ) SELECT IdSotrud, " & _
             intMonth & " FROM tbl where uMonth=" & intMonth -  1 
cmd.ActiveConnection = CurrentProject.Connection
cmd.CommandType = adCmdText
cmd.CommandText = strSQL
cmd.Execute
End Sub