u may can put something like this before your order
this isnt tested so i dont know if syntax is 100%

for (int i=0; i<OrdersTotal(); i++) {
if (OrderSelect(i, SELECT_BY_POS, MODE_TRADES)) {
if (OrderSymbol()==Symbol() && OrderMagicNumber()==Magic) {
OrderClose(OrderTicket(), OrderLots(), Bid, 100, Red);
} }}}


for (int i=0; i<OrdersTotal(); i++) {
if (OrderSelect(i, SELECT_BY_POS, MODE_TRADES)) {
if (OrderSymbol()==Symbol()) {
if (OrderMagicNumber()==Magic) {
OrderClose(OrderTicket(), OrderLots(), Bid, 100, Red);