problem here need assistance

 % I have a program like this
 % starting guess pressure e.g P(1,1)
 % line 1     some program
 %                //
 %                //
 %  error check if it statisfy break the program
 %              else
 %           Assume another pressure 
 %                  P(1,2) ( from a relation considering the values 
 %                           of P(1,1) as well
 %           go back on line 1 with this pressure and repeat the         %error check if satisfy ok if not
 %            Another pressure 
 %            P(1,3) and again go back with this pressure on line 1
 %            this P(1,3) from some relation also satisfy this 
 %            if (log(P(1,3))-log(P(1,2)))<1
 %if (log(P(1,3))-log(P(1,2)))>-1
 %Pcal=P(1,3);

 %else
 %P(1,3)=exp(log(P(1,2))-1);

 %Pcal=P(1,3);

 %end
 %else
 %P(1,3)=exp(log(P(1,2))+1);

 %Pcal=P(1,3);

 %end
 % Can someone help me with this please