passing a query string to a popup window problems

I am trying to pass 2 variable values(username and userpassword) to a popup window to display those values when a button is clicked. When the window pops up, the variable names aren't displayed because they havent been passed. Here is the code: onclick="window.open('http://www.bluedorado.com/bdnfosrc/distributionpopup.p hp?formuser=$formuser&formpassword=$formpassword','BD_Hit_Distribution','hei ght=300,width=600,menubar=0,status=0')";> Any ideas why the values arent being passed?