Disabling right-click behaviour of SpinButton

Hello again gurus,

In my GTKmm 2.24 application, there are some SpinButtons used to control 
the system in various ways. One of our customers complained that the 
up/down steps of one of them were too coarse, which is fair enough as 
that one drives a fairly sensitive piece of equipment that can generate 
really bad sparks and electrical interference and Bad Things if you 
whack it up too fast. So I'm thinking... the default behaviour of 
accepting a right-click on the up spinner as a request for "straight to 
the maximum" is probably a Really Bad Idea for this application.

So, how do I arrange for the right-click on this widget's up-spinner to 
not do anything?

Thanks in anticipation,

Rob