Use of fx:constant in attributes?

Question

I am wondering, is it somehow possible to use <fx:constant> in an attribute instead of a separate tag?

Currently this works for me:

<Label>
    <text>
        <MyController fx:constant="MY_CONSTANT_STRING" />
    </text>
</Label>

while I would prefer something like this:

<Label text="<MyController fx:constant="MY_CONSTANT_STRING" />" /> 

Is something like the later possible?

Thanks for any hint!