How do I modify history.go(-1)?

Hi Experts,

I have:

function BackToShipmentETA()
{
 history.go(-1)
 return true
}

But I want to include Unlock=1 at the end of the URL so depending on what the last web URL was it would look something like this:

http://cabrarn-248kn81.chep.com/intermodal/shipment_tracker/CN_ManageShipments.asp?Emailed=1&Unlock=1"

How can this be done?

Thanks