abdalrhman - if you want to exit out of your loop once the tolerance is less than zero, then put in a condition to do so
for EJ=EJ+.015:.01:E1-.01
Q1=sqrt((E1-EJ)/R1);
Q2=sqrt(abs((E2-EJ))/R2);
Q3=sqrt((EJ-E3)/R3);
tol=Q1-Q2-Q3l
EJ;
if tol < 0
break; % exit loop since tolerance is now negative
end
tolnew=tol;
end
