group_title
A title to be displayed on the group box. If the show_groupbox property is set the title will appear at the top left of the group box. If the group box is not shown the title will appear centered above the group of radio buttons.
Default value
Blank
Valid values
Single-quoted text or the name of a multilingual text variable, system variable or field (the ellipses button in the property sheet can be clicked to choose from a list).