Update decimal value on UpdateEvent in GridView using VB.Net in ASP.Net

Hi

I have issue in updating the nemerical value with decimal using asp.net

here is my code

    Protected Sub gv_RowUpdating(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewUpdateEventArgs) Handles gv.RowUpdating
        Dim dt As DataTable = Session("Grid_Details")
        Dim txtQtyAvail As TextBox = gv.Rows(e.RowIndex).Cells(7).Controls(0)
        Dim reg_exp As New Regex("^\d+$")

        Dim arow As GridViewRow = gv.Rows(e.RowIndex)
        If Not reg_exp.IsMatch(DirectCast(arow.Cells(7).Controls(0), TextBox).Text) Then
            DirectCast(arow.Cells(7).Controls(0), TextBox).Text = "Only number positive"
            DirectCast(arow.Cells(7).Controls(0), TextBox).ForeColor = Drawing.Color.Red
            e.Cancel = True
        Else
            Dim number_pro As Integer = Integer.Parse(txtQtyAvail.Text)
            If number_pro = 0 Then
                dt.Rows(e.RowIndex).Delete()
                dt.AcceptChanges()
                Session("Grid_Details") = dt
                load_Grid_Details()
            Else
                dt.Rows(e.RowIndex)("qtyavailable") = number_pro
                dt.AcceptChanges()
                Session("Grid_Details") = dt
                gv.EditIndex = -1
                load_Grid_Details()

            End If
        End If
    End Sub

I am using Session. below is session code

    Sub CreatGridDetails()
        Dim dt As New DataTable
        If dt.TableName.Contains("tbl_GridDetails") = True Then
            Exit Sub
        Else
            dt = New DataTable("tbl_GridDetails")

            dt.Columns.Add("rmcode", GetType(String))
            dt.Columns.Add("rmdesc", GetType(String))
            dt.Columns.Add("specs", GetType(String))
            dt.Columns.Add("uom", GetType(String))
            dt.Columns.Add("qty", GetType(Decimal))
            dt.Columns.Add("qtyavail", GetType(Decimal))
        End If
        dt.Rows.Clear()
        Session("Grid_Details") = dt
        gv.DataSource = dt
        gv.DataBind()

    End Sub

Normal number like 234 can be entered. but cannot enter 234.90 like this

Pls advice me how to do it

thank you

maideen