How to do an external hierarchy filtering with the ext IO

i need to do this:

A hierarchy of an Infoobject "A". but need FILTERED with the Char "B", example:

-First line of hierarchy

level 1

level 2 "Char B" with value 1

level 3 "A" example = apple

-Second line

level 1

level 2 "Char B" with value 2

level 3 "A" example = pear

to do this i made some time ago an external char in Hierarchy, doing this, when i run the query this show me the hierachy with the levels that i wanted BUT this wasnt filtering with the CHAR "B" for each line, my question is this:

1- The external char in hierarchy just can use it to show values but not to filtering trough them?

2- how can i do this task in my report?, help guys...