[amibroker] SetPositionSize and SigScaleIn - Please Help

[stock99man]

I am trying to set my initial position size to 100 shares. if additional 
conditions are met, I want to add 200 shares, 300 shares, and 400 shares.

I can't get this code to work...it will only do equal amounts of shares for 
each sigscalein.

Can someone PLEASE help?

SetPositionSize(100,spsShares);

Buy=buy rule
Sell=sell rule

priceatbuy=0; 
enter = 0; 

for( i = 0; i < BarCount; i++ ) 
{ 
   if( priceatbuy == 0 AND Buy[i] ) 
    { 
       priceatbuy = BuyPrice[i]; 
    } 

   if( priceatbuy > 0 ) 
    { 
      if( enter == 2 AND Close[i] < priceatbuy) 
       { 
         // add to your position 
         enter = 3;
         Buy[i] = sigScaleIn; 
//         SetPositionSize(400,spsShares);
       } 

      if( enter == 1 AND Close[i] < priceatbuy)  
       { 
         // add to your position  
         enter = 2;
         Buy[i] = sigScaleIn;
//         SetPositionSize(300,spsShares);
       } 

      if( enter == 0 AND Close[i] < priceatbuy)  
       { 
         // add to your position  
         enter = 1; 
         Buy[i] = sigScaleIn;
//         SetPositionSize(400,spsShares);
       } 

      if( Sell[i] ) 
       { 
         Buy[ i ] = 0; 
         enter = 0; 
         priceatbuy = 0; // reset price 
       } 
    } 
}