SQL & PL/SQL :: Multiple Submit Button In A Single Form

My current system have 1 submit button with single form. This submit button will call *file_content.upload*.

htp.p('function on_submit() {');
htp.p('...the rest of my code here..');
htp.p('document.forms[0].submit();');
htp.p('return true;');
htp.p('}');
htp.p('<form enctype="multipart/form-data" method="post" action="file_content.upload">');
htp.p('...the rest of my code here..');
htp.p('<input type="button" id="btn_Submit" value="Submit" onclick="on_submit()"></form>');

My question is, i want to enhance this by adding additional 1 submit button with value "Save". But this new "Save" button will call/trigger different file. This new button will call *file_content.update*. How to accomplish this and how to differentiate these 2 button?

htp.p('<input type="button" id="btn_Submit" value="Submit" onclick="on_submit()"> 
<input type="button" id="btn_Save" value="Save"></form>');