请问各位老师，这段代码怎么不起作用呀？

初学ACCESS，刚做的新增窗体，在判断有重复输入项时弹出警告窗口却没弹出，不知错在哪？请各位老师帮忙解答下，谢谢！

Option Compare Database


Private Sub cmd_Save()
Dim rst As DAO.Recordset
If IsNull(Me.bmmc) Then
MsgBox "请输部门名称!", vbCritical, "提示："
    Me.bmmc.SetFocus
    Exit Sub
End If
Me.Refresh
If IsNull(Me.bmbh) Then
MsgBox "请输部门编号!", vbCritical, "提示："
    Me.bmbh.SetFocus
    Exit Sub
End If
Me.Refresh
If Acchelp_StrDataIsExist("sbglbmxx_child", "部门名称", Me.bmmc) = True Then
    MsgBox "你输入的部门已经存在，请重新输入", vbCritical, "警告"
    Me.bmmc.SetFocus
    Exit Sub
End If
Me.Refresh
If Acchelp_StrDataIsExist("sbglbmxx_child", "部门编号", Me.bmbh) = True Then
    MsgBox "你输入的部门编号已经存在，请重新输入", vbCritical, "警告"
    Me.bmmc.SetFocus
    Exit Sub
End If
Me.Refresh
If MsgBox("您确认要保存吗?", vbOKCancel + vbInformation, "提示") = vbOK Then
Set rst = CurrentDb.OpenRecordset("sbglbmxx_child", dbOpenDynaset)
rst.AddNew
rst("部门名称") = Me.bmmc
rst("部门编号") = Me.bmbh
rst.Update
rst.Close
Set rst = Nothing
'刷新数据
If IsLoaded("usysfrmMain") Then
     DoCmd.Echo False
     Forms!usysfrmMain!frmChild.SourceObject = "frmsbglbmxx_child"
     DoCmd.Echo True
End If
    MsgBox "保存成功!", vbInformation, "提示"
    Me.bmmc = Null
    Me.bmbh = Null
End If
End Sub


Private Sub cmdCancel_Click()
DoCmd.Close acForm, Me.Name
End Sub


Private Sub cmdOK_Click()
 cmd_Save
End Sub

而不是出现