I want to make a statement that 
a buy of croos is valid when another 
  value is above zero
for instance 
Buy=Cross(Graph1,Graph0); 
  is valid if Graph2 <0
and
Sell=Cross(Graph2,Graph0); is 
  valid if Graph1 >0
how can i do that ???
by if and else 
  statement or should i use another one
can you please help me also by 
  giving me direction in this example