I think what you want is:
page1.adp contains...
<img src=@graph_link@>
page1.tcl contains...
set argv1 "dynamicvalue1"
set argv2 "dynamicvalue2"
set graph_link "graph.tcl?[export_url_vars argv1 argv2]"
You can see very similar code in various OpenACS packages. For example, check out workflow-gif.tcl, case-state-graph.tcl, and case-state-graph.adp in packages/acs-workflow/www/
