call popup with string

[Fernando Lobos]

i try call pop via :


var popup12 = mx.managers.PopUpManager.createPopUp(_root,
frm_matriculas, modal, {deferred: true});


all ok !


But this way 


var popup12 = mx.managers.PopUpManager.createPopUp(_root,
frm_matriculas, modal, {deferred: true});


function llama_popup (pop_1:object ){

var popup12 = mx.managers.PopUpManager.createPopUp(_root, pop_1,
modal, {deferred: true});

}

nuevopopup:object

nuevopopup = "frm_matriculas"
llama_popup(nuevopopup)

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nothing, can i do for call popup function with string ?