getMemberlist is not working

I am doing the following:

DS_4.setvariableValueext("group",value);

ds_4.loaddatasource();

dropdown_1.setItems(ds_4.getmemberlist("customer",memberpresentation.external_key,memberdisplay.text,1000));

In the dropdown I  get all the customers instead of just the customers from the group in the variable selection.

When I add a crosstab for the dataset Ds_4, the data is restricted to the group.  I am not sure if I have a misunderstanding of how this works or missing something.  I am on version 1.6.

Any help is appreciated

John Coudriet