How to execute function on all bits of a bus and return result with same family hierarchy

The problem is as follows:

After the transient simulation, I have a bus signal like VT("/a<4:0>").

For simplicity let's say I want to get sum of waveforms of all bits of the bus VT("/a<0>")+VT("/a<1>")...

So I want to write a calculator function that takes the bus as an argument and returns a waveform that is a sum of bits (for example)

sum=mybussum(VT("/a<4:0>"))

The problem is, that each bit may be a multilevel sweep (family of family of family...)

I am generally know how to unwrap all levels of family and sum all waveforms using something like famValue(mywave car(famGetSweepValues(mywave)))

But then, the result has a different structure from the input (and probably will not work for sweeps). I would like to preserve the structure (the result has the same families/sweeps as input) so the function will be more generic.

Will be glad to get suggestions on how to do this.

Thanks.