Unlock the VCS and double click the widget to edit it.
From the Options menu of the Virtual Control Surface Editor select Set tic marks and labels.
Where it says "Select a labeling scheme" select "Code".
Click Edit for a window shere you can enter a Smalltalk expression that evaluates to an OrderedCollection of strings. The default example is
0 to: 4 collect: [:n | 'label' & n]