OnClick event of Button control calling code-behind SUB method

I manually created a button control in a GridView control like this, in VS 2005 (FW2.0):
<asp:TemplateField SortExpression ="Register" HeaderText="">
<ItemTemplate >
<asp:Button ID="btnReg" runat ="server" Text="Register" OnClick ='btnReg_Click(<%#Eval("AvailKeyNo")%>, <%#Eval("ActvNo")%>, <%#Eval("ClassNo")%>)' />
</ItemTemplate ...