With a block I mean a group of assets, 100 in your case. So the idea is to change the 'dow()' condition in your script by a time/date condition, for example like:
if(year(Bar) == 2001)
{
asset("A");
vars price1 = series(priceClose());
asset("B");
vars price2 = series(priceClose());
asset("C");
vars price3 = series(priceClose());
}
else if(year(Bar) == 2002)
//Call another block, etc..