Finding GridPanel in a TabPanel

We have a Tab Panel with multiple tabs and each tab has a its own Grid Panel. I need to refresh/reload the grid control on tab activation. Please let me know how we can find a grid panel from a active tab (tabid)

Code:

---

<ext:TabPanel ID="MainTabPanel"  runat="server">                             
<ext:Tab ID="Tab1" Title="Tab1" runat="server" Closable="true">
    <ext:GridPanel="Grid1" runat="server">
</ext:GridPanel>
</ext:Tab>
<ext:Tab ID="Tab2" Title="Tab1" runat="server" Closable="true">
    <ext:GridPanel="Grid2" runat="server">
</ext:GridPanel>


</ext:Tab>


 </ext:TabPanel>

---

Thanks,

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