Dynamic rollup expression in listbox?

[#1]

I am trying to persuade the list box to display an aggregate and a field something like this:

(133) Asia

(76) Europe

(90) North America

...

I have not found that magic expression that will make this happen.

I have tried two approaches: constructing a field that when evaluated will yield the desired value and using a variable with a parameter that will evaluate to the desired value:

Variable expression in list box:

=$(vDynaRollup((Place)))

Variable defined as:

SET vDynaRollup = '('&Sum({$<Ancestor={$1}>}Count)&') '&$1;

Evaluation of field in list box expression:

=$(=[Rollup])

Example value of Rollup:

Sum({$<Ancestor={'Argentina'}>}Count)&' Argentina'

Either of these attempts results in a list box with no contents.

As a second best attempt, I tried adding an expression evaluating either the variable or field to a list box displaying just a field and while it work (field values are displayed), the sum is always zero.

Can a list box expression be used to display a rollup aggregate or am I SOL?

(See attached for an example.)