Value of Select Box

[admin]

I am trying to get the value of a select box (set to multiple).

I have tried:
document.all.FormName.FormField.selected.value
AND
document.all.FormName.FormField.value

But neither seem to work. Basically what I am trying to do is use a Javascript funtion to submit a go to another page (using location.href('....')), with the value of a select box appended to the url as a url variable, but I just keep getting an error "Object doesn't support this property of method".

function down(){
location.href('index.cfm?report=repname&parent='document.all.FormName.FormField.selected.value);
return true;
}


Thanks in adance.