Etwas

set choice [lcdui.choicegroup -label choice -type exclusive]
$choice append a
$choice append b

set returnval -1
proc Handler {cmd form} {
	global returnval choice
	set selected [$choice selection get]
	if {eq [lindex $selected 0] 1} {
		set returnval 1
	} else {
		set returnval 0
	}
}

set form [lcdui.form -title test -commandaction Handler]
$form append $choice
$form addcommand [lcdui.command -label go -longlabel go -type screen]

$form setcurrent
set returnval