VB 2010 sendkeys错误

Imports System.Runtime.InteropServices

Public Class Form1

    Private Sub Button2_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Application.Exit()
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim ProcID As Integer
        ProcID = 2940
        AppActivate(ProcID)
        SendKeys.SendWait("Username")
        SendKeys.SendWait("{ENTER}")
        SendKeys.SendWait("Password")
        SendKeys.SendWait("{ENTER}")
    End Sub
End Class

错误: