关于DataGrid1控件的更表问题！高手进！

问题如下图所示
实现功能是：单击审核按钮进根据所查询的入库单号，在“是否审核”列中自动填入“审核”二字，以下是我个人写的代码：Private Sub Command2_Click()
Dim sql As String
Dim str As String
Dim Conn As ADODB.Connection
Dim rst As ADODB.Recordset
str = "Provider=SQLOLEDB.1;Password=sa;Persist Security Info=True;User ID=sa;Initial Catalog=UF2011;Data Source=server"
Conn.ConnectionString = str
Conn.Open
Set rst = New ADODB.Recordset
sql = "select * from salary"
DataGrid1.Columns(8).Text = "审核"
rst.CursorLocation = adUseClient 
rst.Open sql, Conn, adOpenDynamic, adLockOptimistic
Set DataGrid1.DataSource = rst
DataGrid1.Refresh
End Sub

执行时
就会跳到 Conn.ConnectionString = str 这一行！提示，实时错误'91'..对象变量或with块变量未设置 .......烦请各位高手帮帮忙，或者各位有更好的代码能实现这个功能请烦写一下哈....谢谢了！

VB code

在
Conn.ConnectionString = str
前,加一句:
Set Conn = New ADODB.Connection

Dim Conn As new ADODB.Connection