The Formula property will be used to calculate a value and that value will be set on a property of the control as indicated by the PropertyName property. If PropertyName has not been set or is set to an invalid property, then no calculation will take place.
It is strongly recommended that any element with a formula be marked ReadOnly. A control that is the target of a formula calculation should not be edited by the end user, because any user-edited value will be overwritten by the calculated value. Also, if an element is used as both the target and the source of a formula, then the source value will always use the calculated value and not the value displayed in the control after a user's edit.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2