怎样直接把textbox中（时间）内容作为条件在sql中引用

Protected Sub Button2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim name As String
        name = Server.MapPath("财管.mdb")
        Dim lian As OleDbConnection = New OleDbConnection("PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA Source=" & name)
        lian.Open()
        Dim sql4 As String
        Dim a As Date
        sql4 = "select sum(消费额) as 和 from 消费 where 时间='"textbox1.text"'"
        Dim ming4 As New OleDbCommand(sql4, lian)
        Dim read4 As OleDbDataReader = ming4.ExecuteReader
        read4.Read()
        TextBox3.Text = read4("和")
        lian.Close()
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        TextBox1.Text = Today
    End Sub

该段代码中sql4 = "select sum(消费额) as 和 from 消费 where 时间='"textbox1.text"'"
这一句错误，请问各位大侠怎样直接把textbox1.text的内容作为条件在sql中使用
谢谢