New window launched by form needs scrollability

[wxdqz]

I'm just a lowly cut-and-paster. Any of you js-heads out there help me with this? I am launching a new window upon submittal of a form with the following script, and I want to make that window scrollable. How would I do it? I thought that I could add the comment "scrollable," to my form target attribute, but that seems to have no effect. Also, how can I get this new window to launch in the center of the screen instead of top left? Any suggestions are appreciated.

target="_new:width={250},
resizable,
scrollable,
height={350},
status"
onSubmit="return createTarget(this);">


function createTarget(form) {
_target = form.target;
_colon = _target.indexOf(":");
if(_colon != -1) {
form.target = _target.substring(0,_colon);
form.args = _target.substring(_colon+1);
} else if(typeof(form.args)=="undefined") {
form.args = "";
}
if(form.args.indexOf("{")!=-1) {
_args = form.args.split("{");
form.args = _args[0];
for(var i = 1; i < _args.length;i++) {
_args = _args.split("}");
form.args += eval(_args[0]) + _args[1];
}
}
form.args = form.args.replace(/ /g,"");
_win = window.open('',form.target,form.args);
if(typeof(focus)=="function")
_win.focus();
return true;
}