You can restrict your solution conditionally by using the OPTIMIZE option on the SOLVE statement. Below is an example of a simple case where only the solution for the 9th observation is restricted to be less than or equal to 8. Please let me know if you had something else in mind.
data d;
do t=1 to 10;
output;
end;
run;
proc model data=d;
y = t**2/10;
solve y / optimize out=o;
restrict ifn(t=9,y,0) <= 8;
quit;
proc print data=o;
run;