Javascript to pass variables to anothe html page

I need a java script creating (from scratch) or an exisiting one ammending so that it pushed the selction a user makes from a drop down list onto the destination page. i have found a script that does this at the moment which can been seen here; [login to view URL] i need for the script to be amend so that it's just one line (the simple bit) and the variable that i want to push through to be called 'Unlock' at the moment there 3 variables (firstname. lastname,age) i want them all remove and only one variable ('unlock'). 2nd - if nothing is passed the destination pages says (undefined). I want it so that if nothing is passed then nothing is displayed on the destination page. Lastly, i want to also intergrate this with google ads so that google can pass dynamic keywords to it, e.g [login to view URL]{google keyword}. You can amend the existing scrip or create a new one.