using a variable in a JS dot notation string

I have a Javascript function in my PHP page that I need to plug a variable into, and for the life of me I can't figure out how to do it. This is the hardcoded version that works: rBvalue = document.voteForm.Test_Amendment_One[0].checked In the above example the "Test_Amendment_One" is the value I would like to pass in a varaible: $tempVar = "Test_Amendment_One" rBvalue = document.voteForm.($tempVar)[0].checked Obviously that doesn't work...what syntax should I use to correctly make this work? Thanks, Ron