// event function - called when changing value in dialog
static bool gender_choose_event(TreeNode& myTree, int nRow, int nType, Dialog& dlgGetNBox)    
{
	TreeNode tn;
	
    if(nRow < 0) // On dialog init, nothing to do
        return false;
 
	if(true)  // <-- missing the type: TRGP_RADIO_INDEX why doesnt exist??
	{
		tn = myTree.GetNode("gender");
		if(!tn)
			return false;
		
		// changing value of the radio button
		tn.nVal = 0;
		tn.nVal = 1;
		tn.nVal = 2;
		
		return true;
	}
	return false;
}
void GetNBox_ex2()
{
    GETN_TREE(myTree)
    GETN_RADIO_INDEX(gender, 0, "male|femal|other")
 
    if( GetNBox(myTree, "gender", "what have you got", NULL, gender_choose_event) )
    {
    	// do something
    }
}