There is a new attribute for the @GetViewInfo in the Notes and Domino 8 Public Beta 2.

[IsViewFiltered]
Returns True (1) if the @SetViewInfo command has been used to limit which documents are displayed in the view, False (0) otherwise. This is useful in hide formulas for view actions.

It is not documented in the Notes 7 Designer Help, but it is used in the mailtemplate I’ m using with my 7.0.2 client. According to the Hide-When formula of the “Unfilter” action in the ($Calendar) view, the attribute should work with Notes versions from 7.0.1 and above.

OkToShow := @If(@Version < @Text(258);  0; @GetViewInfo([IsViewFiltered]); 1; 0);