SYS(2021) - Filtered Index Expression


>Hello Everybody ,
>I need to get from a table the expression for and index with a filter,
>KEY() only returns the expression part, not the filter part.
>Example,if I do something like :
>INDEX ON CaseNumber FOR CaseStatus="O" TAG OpenCases
>KEY(1) return "CaseNumber", but, it doesn't tell me the 'FOR CaseStatus="O"' part.
>
>Any Ideas ?
>
>=THIS.Thanks("in advance")