Ask price showing on chart with slight delay

[Dark Ryd3r]

I am using code

   MqlTick last_tick;
   SymbolInfoTick(_Symbol,last_tick);
   
   double Askx=last_tick.ask;
   Comment("", Askx);

to calculate Ask price, but its showing with slight delay as compared to Marketwatch chart

How can i calculate it on real time?

Thanks