รบกวนพี่ ๆ ดูให้ทีครับ Error converting data type varchar to float.

 Public Sub combobox_province()
        'Dim conn As New OleDb.OleDbConnection("Provider
        Dim txt As String
        Dim adapter As New SqlClient.SqlDataAdapter
        Dim ds As DataSet = New DataSet
        txt = "SELECT * FROM db_province order by pro_id asc"

        adapter.SelectCommand = New SqlClient.SqlCommand(txt, cn)
        adapter.Fill(ds)
        combo_province.DataSource = ds.Tables(0)
        combo_province.ValueMember = "pro_id"
        combo_province.DisplayMember = "pro_name"
    End Sub
    Public Sub combobox_aumphor()
        Dim txt As String
        Dim adapter As New SqlClient.SqlDataAdapter
        Dim ds As DataSet = New DataSet
        txt = "SELECT * FROM db_aumphor where pro_id = '" & combo_province.SelectedValue.ToString() & "' order by aum_id asc"

        adapter.SelectCommand = New SqlClient.SqlCommand(txt, cn)
        adapter.Fill(ds)
        combo_aumphor.DataSource = ds.Tables(0)
        combo_aumphor.ValueMember = "aum_id"
        combo_aumphor.DisplayMember = "aum_name"
    End Sub
    Public Sub combobox_tumbon()
        Dim txt As String
        Dim adapter As New SqlClient.SqlDataAdapter
        Dim ds As DataSet = New DataSet
        txt = "SELECT * FROM db_tumbon where aum_id = '" & combo_aumphor.SelectedValue.ToString() & "' order by tum_id asc"
        adapter.SelectCommand = New SqlClient.SqlCommand(txt, cn)
        adapter.Fill(ds)
        combo_tumbon.DataSource = ds.Tables(0)
        combo_tumbon.ValueMember = "tum_id"
        combo_tumbon.DisplayMember = "tum_name"
    End Sub
    Private Sub combobox_zippost()
        Dim txt As String
        Dim adapter1 As New SqlClient.SqlDataAdapter
        Dim ds As DataSet = New DataSet
        txt = "SELECT * FROM db_tumbon where tum_id = '" & combo_tumbon.SelectedValue.ToString() & "' order by tum_id asc"
        adapter1.SelectCommand = New SqlClient.SqlCommand(txt, cn)
        adapter1.Fill(ds)
        cust_zipcode.DataSource = ds.Tables(0)
        cust_zipcode.ValueMember = "tum_id"
        cust_zipcode.DisplayMember = "zippost_code"
    End Sub