How do I wire up a custom button (non Select, Edit, Delete) in a datagrid that is a template column?

[AMT2K5]

For example I have

<asp:button OnClick="RentMovie_Click" id="rentMovie" Text="Rent it!"
runat="server" CausesValidation="false" CommandArgument='<%#
DataBinder.Eval(Container, "DataItem.MovieID") %>'
CommandName="rentMovie">
</asp:button>

I need to pass DataItem.MovieID to a subroutine called RentMovie_Click
but I am unsure on what the prototype for that subroutine should look
like, as in what its arguments are and handler

Appreciate any help.