From Xojo Documentation
The caption of a checkbox.
This property can be set inside the IDE or programmatically.
To set an accelerator character, precede the character in the Caption with an ampersand. In order to show an ampersand in the Caption, use two ampersands in a row.
This code sets the caption of the control to "OK".
This code in the Pressed event handler for a DesktopButton changes the text of the button each time it is clicked: