how to clear textbox which is in grid

i have dropdownlist which contains options like(2,3,4)
gridview contains textbox
<asp:GridView ID="GrdOptions" runat="server" AutoGenerateColumns="False" Width="212px" >
<Columns>

<asp:TemplateField HeaderText="Option" HeaderStyle-HorizontalAlign="Center">
<ItemTemplate>
<asp:TextBox ID="txtText" runat="server" MaxLength="2000" Width="250px"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
Depending on dropdown options gridview will open
if ddlist is 2 then
gridview will open 2 textboxs


1)now how to clear textboxs in grid
2)ho to keep validation
if ddlist is 3, gridview will open 3 textboxs
if i fill 3 textboxs it is ok but if 0 or 1 or 2 it should show message in label or messagebox to fill all options

kaja srinivas