CheckboxState Property
Returns or sets a Boolean value that indicates whether a check box in a smart document is selected. Setting this property to True selects the check box. Setting this property to False clears the check box. Read/write Boolean.
expression.CheckboxState
expression Required. An expression that returns a SmartTagAction object.
Remarks
For more information on smart documents, see the Smart Document Software Development Kit on the Microsoft Developer Network (MSDN) Web site.