Using server tags in custom controls

Hello,
I am having a small problem getting server tags to work in custom controls. What I would like to do is something like this
<custom:Control runat="server">
<% for(int i=0; i<5; ++i) { %>
<%= i %>
<% } %>
</custom:Control> 
But I cannot get this to work. I have been searching for a solution for days now, and have been given advice to use ITemplate
but I have found nothing similar. I am starting to wonder if this is possible at all. But seeing this is possible to do in ContentPlaceholders
there should be a way to solve this. Has anyone done this before?The ultimate goal is to make ...