Bus elements with multiple dimensions

I have a structure S with three time series fields a, b and a.

S.a = timeseries
S.b = timeseries
S.c = timeseries

I'd like to create a bus object (B) with above bus element. But instead of creating 3 bus elements (a, b and c) I'd like to create one bus element (S) with dimension of 3. I created the bus B like this:

S            = Simulink.BusElement;
S.Name       = 'S';
S.Dimensions = 3;

B          = Simulink.Bus;
B.Elements = S;

How can I assing (sub)bus elements (a, b and c) to S (and B)?

@Mark McBroom