Available Bandwidth to be measured

I would like to capture the Availability Bandwith in graph.

as a work around I did enabled the available Bandwidth using offset.

Where #A has been captured from ifHCInOctets

alias(scale(offset(#A, -2400000000.00), 1), ‘Available B/w’).

By doing the above thing, I could able to get the Available B/w values. but not captured on graph.
Can any one help in assiting to plot the graph for Available Bandwidth.