jQuery Grid Plugin - jqGrid

There are already 14 options defined in sopt, and each of the option can be mapped to a sql operator. But it looks like none of them can be mapped "is not null" easily. So I got a requirement of adding "not null" (has data) option in my application.

I have these mapping coded in my source. And sql statement will be generated automatically based on a selected sopt option. Any suggestion about adding the "not null" option? My idea is that I have to modify the jqgrid source file to add one more option to define the "not null" option. Any other ideas?

   protected static final String[] sopt   = {"eq","ne","lt", "le", "gt","ge", "bw",            
      "bn",                
      "in",   
      "ni",                   
      "ew",     
      "en",
      "cn",
      "nc"};
                                
   protected static final String[] sqlopt = {"=", "!=", "<", "<=", ">", ">=", " LIKE 'val%' ",
      " NOT LIKE 'val%' ",
      " IN (val) ",
      " NOT IN (val) ",
      " LIKE '%val' ",
      " NOT LIKE '%val' ",
      " LIKE '%val%' ",
      " NOT LIKE '%val%' "};

Best regard.