Support for mutually-exclusive selection in multi-occuring slot

[nb-programmer]

For example:

%[&request_agg](100)
    [~[i need?]|what is] [the?] @[aggregation][ and @[aggregation]?][\??]

@[aggregation]
    average [value?]
    median [value?]
    minimum [value?]
    maximum [value?]

~[i need]
    [&i]['d| would?] [need|want]
    [&i]['d| would] like
    give [me?]

aggregation occurs twice (since slot type list is possible in RASA). I want it to not use the same slot value for both occurrences in the same sentence. Example:

what is minimum and maximum?

Is correct, but:

what is maximum and maximum?

is not. How do I do this using the DSL rules?