这里面不断抛出错误，实时错误 91，为什么？

Question

Public Username As String

Private Sub cmdCancel_Click()
OK = False
Me.Hide
End Sub

Private Sub cmdOK_Click()
'用来存放SQL语句
Dim TxtSQL As String
'用来存放记录集对象
Dim mrc As ADODB.Recordset
'用来存放返回信息
Dim MsgText As String
Username = ""
'判断输入用户名是否为空
If Trim(txtUserName.Text = "") Then
MsgBox "请输入用户名！", vbOKOnly + vbExclamation, "警告"
txtUserName.SetFocus
Else
'查询指定用户名的记录
TxtSQL = "select * from user_Info where Username ='" & txtUserName.Text & "'"
'执行查询语句
Set mrc = ExecuteSQL(TxtSQL, MsgText)
If mrc.EOF = True Then
MsgBox "该用户不存在！", vbOKOnly + vbExclamation, "警告"
txtUserName.SetFocus
Else
'判断输入的密码是否正确
If Trim(mrc.Fields(1)) = Trim(txtPassword.Text) Then
OK = True
mrc.Close
Me.Hide
Username = Trim(txtUserName.Text)
Else
MsgBox "密码输入错误！", vbOKOnly + vbExclamation, "警告"
txtPassword.SetFocus
txtPassword.Text = ""
End If
End If
End If

End Sub

这里面不断抛出错误，实时错误 91，对象变量或with块变量未设置，调试出错的部位为If mrc.EOF = True Then，请问是怎么回事，该怎么解决？在线等。
具有该怎么操作呢，我刚接触VB不久，对它没有太多的认识。
调试ExecuteSQL返回的是mrc.EOF = <对象变量或with块变量未设置>

Answer 1

mrc 定义的是私有变量在执行 ExecuteSQL(TxtSQL, MsgText)它怎么返回记录，除非把mrc通过参数带进去

Answer 2

调试ExecuteSQL返回的什么