JQGrid - disable checkbox based on value

Question

I would like to disable a checkbox in JQGrid where "multiselect: true" is set.

It was touched on here:

http://stackoverflow.com/questions/1356990/disabling-checkbox-in-multiselecttrue-mode-for-a-specific-row-in-jqgrid

but I'm not sure how to implement this solution since I am new to jqgrid.

im looking to do something like

if (amount > 50) { disable checkbox }