Query Designer Variable in dropdown box

Dear All

I have a a dropdown box in a Design Studion Dashboard which should select a Query Variable.

at the "on select" of the drop down box  Iam trying to type in this code ( see below - I wrote it simila to normal filter ) but it does not work - Which code shall I write?

What shall I write on start up?

Can you suggest good link-tutorial where I can find some codig examples ?

DS_TABLE3.getVariableValueExt("EAZVMU01",DROPDOWN_3.getSelectedValue());

thanks in advance and regards

MAnu