Different graph legend based on selection

Hi guys,

is it possible to change the field being usesd based on the selection from a filter?

I.E.

our business unit hierachies are set up differently from BU to BU.

I need to have value by date for each focus area within a selllected  BU.

BUT BU 1 has the focus area at level 4 and for BU 2, its at level  5(sub-tradng area).

When I select BU 1 in  filter, I need it to show level 4(focus area). if i seelect BU 2 i need it to show level 5(subtrading area.

Is this possible?

even if i have 2 graphs on top of each other. and hide the respective garph based on my selection?

ny ideas?

cheers

Ian