Javascript - Controlling the page that displays

We had a button developed that basically launches the New Opportunity form from a report.  The javascript looks like this:

<button type="button" onclick="window.location='https://secure-vmsomxjza.crmondemand.com/OnDemand/user/OpptyCreateNewPageDefault?OMRET0=OpportunityHomePage&OCTYPE=&OMTGT=OpptyCreateEditForm&OMTHD=OpportunityNewNav'">New Opportunity</button>

The opportunity form opens and it operates fine.  We didn't want a new window to open or a new tab in the current session.  However, as you can see in the attached, it duplicates the action bar and crm header/tabs/etc.  Is there a way to add a command on the java script so only the form itself opens and basically looks like the normal screen you would see if using the New button from the usual opportunity screens?