Syntax error converting character string to smalldatetime data type

Hello experts@!@

I have this large datagrid...which displays about 1000 items from a SQL DB...as of right now, when the visitor comes to the page the whole sql table is produced before them.

What I would like to do is make a UI that will allow the user to display portions of the SQL-table based on different criteria.

Right now all I'm concerned with is getting it so the user can put a date range into two texboxes, but i'm having trouble getting around the error:

Syntax error converting character string to smalldatetime data type

Why is the code below generating that error? What am I doing wrong?   -thanks -neo

Code:

    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Put user code to initialize the page here
    End Sub
   
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Try

            Dim highdate As DateTime
            Dim lowdate As DateTime
            lowdate = Format(Convert.ToDateTime(Me.txtDate1.Text), "MM/dd/yyyy")
            highdate = Format(Convert.ToDateTime(Me.txtDate2.Text), "MM/dd/yyyy")
            Const strConnString As String = "connection string omitted"

            Dim objConn As New SqlConnection(strConnString)
            Dim strSQL As String
            strSQL = "select * from webdocuments where (((datefiled) > 'lowdate') and ((datefiled) < 'highdate'))"

            Dim mycommand As New SqlCommand(strSQL, objConn)
            objConn.Open()
            DataGrid1.DataSource = mycommand.ExecuteReader(CommandBehavior.CloseConnection)
            DataGrid1.DataBind()


        Catch ex As Exception
            Dim strScript As String
            strScript = "<script language=javascript>"
            strScript &= "alert('something went wrong');"
            strScript &= "</script>"
            If (Not Page.IsStartupScriptRegistered("clientScript")) Then
                Page.RegisterStartupScript("clientScript", strScript)
            End If
        End Try
    End Sub