jQuery Grid Plugin - jqGrid

(From my stackoverflow.com question, posted here):

I'm using v4.0 and n my ASP.NET MVC 3 app, I've got pages with jqGrids on them. I've customized the search operations on a per-column basis like so: 

colModel: [
   { name: 'IceCreamName', index: 'IceCreamName', align: 'left',
     searchoptions: {sopt: ['eq', 'ne', 'cn']} },
.
.
.
   { name: 'InitialDate', index: 'InitialDate', align: 'left',
     searchoptions: {sopt: ['eq', 'ne', 'gt', 'lt', 'ge', 'le']} },
   { name: 'Volume', index: 'Volume', align: 'left',
     searchoptions: {sopt: ['eq', 'ne', 'gt', 'lt', 'ge', 'le']} }

]

And that'll give me, for this example, Equal, NotEqual, Contains on the name, and Equal, NotEqual, 
GreaterThan, LessThan, GreaterThanOrEqual and LessThanOrEqual on the date and volume columns. 
Wonderful. That customization is great.
What I'd particularly like to do though is customize the strings displayed in the search operation dropdown 
for those columns. For instance, for the InitalDate column, I'd like the 'gt' to display "after"instead of "greater" 
(makes more sense to the user) and something like "on or before" instead of "less or equal".
I see that I can modify those globally in the grid.locale-en.js (or whatever locale is correct) but that is at a 
global level. I'd like the date and volume columns to have strings that are specific to those columns.
Any way to do that? Perhaps I missed something in the documentation on how to accomplish that but it is my understanding, 
according to a response on SO by Oleg that it isn't built-in.  He provided an example extension to this which I'm looking at now.

Thanks,
Matt