Compare today's Account balance to yesterday's

[vishnurama]

Guys , Here's what I want my code to verify before going through each iteration(on tick). 

if ( //AccountBalance is >= 5% than yesterday's ) {
      // return;
   } else {
      // starttrading();
   }

But the question is , how do I compare it to yesterday's account balance ? How do I put it in code ?

Any ideas would be highly appreciated.

Thanks,