access提示编译错误，子过程或函数未定义

Private Sub Form_Load()
On Error GoTo Err_Command_Click
 '判断用户窗体是否导入数据了
  If IsLoaded("用户登陆") Then
  
    List12.RowSource = "SELECT DISTINCT 用户表.用户名 FROM 用户表 WHERE " _
                 & " (((用户表.用户名)<>'" & Forms("用户登陆").cboUserName.Value & "' " _
                 & " and (用户表.用户名)<> 'CG2008')) ORDER BY 用户表.用户名"
  Else
    List12.RowSource = "SELECT DISTINCT 用户表.用户名 FROM 用户表 where " _
                & " 用户表.用户名<> 'CG2008'  ORDER BY 用户表.用户名"
  End If
  List12.Requery
List12.SetFocus
Command9.Enabled = True '新建
Command10.Enabled = False '
Command11.Enabled = False
Command15.Enabled = False '取消

Text1.Locked = True
Text2.Locked = True
Exit_Command_Click:
    Exit Sub

Err_Command_Click:
    MsgBox Err.Description
    Resume Exit_Command_Click
End Sub

提示错误的地方是:IsLoaded   请大家帮忙看看  谢谢