Web Forms :: Using Timer Control For Incrementing Variable?

Here upon loading the page there will be 4 panels having their own timer controls (having interval 1000) for incrementing a variable "a". But the problem is that, as I have used static variable that's why all the timer's are sharing the variable "a" and creating a problem like each panel's label showing a value incremented by 4 after every second. Can any body solve this problem..

<asp:ListView DataSourceID="sqldtsrclivepdt" ID="livepdtlst" runat="server">
<LayoutTemplate>
<ul class="productlist">
<asp:PlaceHolder ID="itemPlaceholder" runat="server"></asp:PlaceHolder>
</ul><br />
</LayoutTemplate>
<ItemTemplate>
<li>
<asp:Panel ID="pnllivepdt" CssClass="paneldesign" runat="server">
<asp:UpdatePanel ID="updtpnlbid" runat="server">
<ContentTemplate>
<asp:Label ID="lblbidtimer" runat="server"></asp:Label><br /></ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="tmrpnl" EventName="Tick" /></Triggers>
</asp:UpdatePanel>
<asp:Timer ID="tmrpnl" Enabled="true" Interval="1000" OnTick="tmrpnl_Tick" runat="server"></asp:Timer>
</asp:Panel>
</li>
</ItemTemplate>
</asp:ListView>
static int a=0;
protected void tmrpnl_Tick(object sender, EventArgs e)
{
Timer tm = sender as Timer;
Panel p = tm.Parent as Panel;
Label lt = p.FindControl("lblbidtimer") as Label;
a++;
lt.Text = a.ToString();
}