Remove numerous trailing commas from text string that contains commas

I am trying to get a formula or macro that will remove all the trailing commas from a single row while leave the ones in the string as is. Excel 2010

Ex;

2-Way Ball Valves, 2-Way Flow Valves, Ball Valves, CPVC Ball Valves, Shutoff Valves, , , s/b

2-Way Ball Valves, 2-Way Flow Valves, Ball Valves, CPVC Ball Valves, Shutoff Valves

The amount of text in each row varies (could be more/less terms)

This formula has been suggested; but I still see the commas when i drag down

=LEFT(B2,LEN(B2)-1)&SUBSTITUTE(RIGHT(B2), ",", "")

Any help is very much appreciated! Thank you!!