Accept requotes automatically

The key is "try and try again".

Roughly like this:

while (tries < 3)
   {            
   ticket = OrderSend(Symbol(),OP_SELLLIMIT,lotsize,openprice,Slippage,st,tp,"Order",magicnr,0,Red);              
      if(ticket<=0) {//Order not accepted
      tries++;
      } else tries = 3;
   }

Make sure your RefreshRates() call is as near as possible before your OrderSend(). You don't want to be doing a whole lot more time consuming processing in between.

And perhaps increase your slippage? :-)

Yes I forgot about that.

In addition, especially if you're scalping, check that prices are still acceptable before trying once more to force the order through...

On the first try you might have an indicated profit, but on the next try, or the try after that, the priced may have changed too much.

Also add a pause of about 3secs between each try otherwise you may get out of sync with the replies from the trade server.... this is

if you send the next try on the next tick.

If instead you fire from a loop as suggested above the pause is 'mandatory' otherwise you'll just be sending (3) simultaneous requests

which of course is nonsense.

How do you pause in MT4 code?

Sleep()

Look at https://docs.mql4.com/common/Sleep