AutoCAD 2013 :: Protect Lisp Functions From Object ARX

I would like to protect lisp functions from ObjectARX. I am able to protect the functions from LISP command prompt as below.

(pragma '((protect-assign MyFunction)))

I want to do it programmatically using ObjectARX. I have written below code but I am getting error "some other error". 

struct resbuf *cmdlist;
resbuf *rb_out = NULL;
cmdlist = acutBuildList(RTSTR, _T("pragma"),RTSTR, _T("protect-assign"),RTSTR,_T("MyFunction"), 0);
int resval = acedInvoke(cmdlist,&rb_out);
if (RTNORM != resval)
{
acedAlert(_T("Error"));
}
acutRelRb(cmdlist);