how to Enable/disable covergroups with in classes

Hi,

Need to Enable/disable covergroups defined with in classes with out changing instantiation of those done using new()

E.g. 

class c2 extends base; // class c2 includes covergroup
int cov1;
covergroup cg@(posedge clk);
coverpoint cov1;
endgroup
function new(string obj_name);
cov1 = 1;
cg = new;
cg.set_inst_name({obj_name,".cg_inst"});
endfunction
endclass

c1 o1;
c2 o2;
...
o1 = new; //object of class c1
o2 = new("o2"); //object of class c2
o1.b1 = o2; //object of class c2 assigned to a member of class c1 (o1.b1)
o2 = null;
...

Is there any way to enable/disable covergroup cg without modifying above code?

THanks