Im kinda new to this programming stuff so this is probably a really easy question. How do i get my robot to react to a increase or decrease of 20 points from my sharp IR. Right now  my code looks like this (b1 is IR reading)
if b1 > 115 then
 gosub TURNRIGHT
 end if
 if b1 < 85 then
 gosub TURNRIGHT
 endif
 my sensor reads about 95 when its on my black table but with different light sources or materials it can jump up or down. Instead of using 85 and 115 in my code i want it to react whenever there is a change of a specified amount.
             
            
              
              
              
            
            
                
                
              
           
          
            
            
              You need 2 readings
In order to note the change in readings. Use a variable (e.g. b2) to remember the last reading. Set the var to the last reading before you take a new one. use b3 (or something) for the difference
getreadings:
	b2=b1 
	readadc 0,b1 
return
----- SOME OTHER CODE — 
if  b2>b1 then
	b3=b2-b1
else
	b3=b1-b2
endif
if b3>20 then
	gosub TURNRIGHT
endif
or something like that
             
            
              
              
              
            
            
                
                
              
           
          
            
            
              Perhaps use a reference
Perhaps use a reference variable. Get that stored on the surface the robot is operating on. Think maybe using another B variable can work, storing in B2 maybe. Then try 
if b1 > (b2 + 20) then
 gosub TURNRIGHT
 end if
 if b1 < (b2 - 10) then
 gosub TURNRIGHT
 endif
 Or even :
if b1 > (b2 + 20) OR b1 < (b2-10)  then
 gosub TURNRIGHT
 end if
Note that this may not be standard PICAxe Basic, so a reference to the manual regarding expessions and boolean logic might be needed.  
 
             
            
              
              
              
            
            
                
                
              
           
          
            
            
              picaxe basic limits
Thats one of those irritating things about picaxe basic: no calculations in conditions
             
            
              
              
              
            
            
                
                
              
           
          
            
            
              That woked great, thanks!
That woked great, thanks!