Customizing the metamodel : Keywords for USRPROPS : BUTTON and TARGETPROP
  
BUTTON and TARGETPROP
The BUTTON keyword defines a button that will execute a macro.
The function must have the following parameters and visibility:
Public Function routinename(ByVal strPropName As String, ByVal lngDDID As Long, ByVal strPrevValue As String, ByVal strValue As String, ByRef varRet As Variant) As Long
strValue is current value.
varRet receives the value to be written to the property identified by the TARGETPROP keyword, which is optional.
Example
script
Property "propname" {Edit Button TargetProp "Content" Macro macroname.modulename.routinename }