do you mean, you want to trade only after 00:00 O'clock of your gmt 12 time?

anyway

1st you need to know the server time

then convert it to the gmt time

and use the iTime(Symbol(),PERIOD_D1,0) as a reference ,
it's the 00:00 O'clock of the server time

if server time is on gmt +2
then only allow to trade only after iTime(Symbol(),PERIOD_D1,0)+(10*60*60)

like

if(CurTime()>iTime(Symbol(),PERIOD_D1,0)+(10*60*60 ))
{
OrderSend(.....);
}

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hope it helps