options nocenter ps=60 ls=75;
goptions reset=all;

data example;
 input trt block resp @@;
 cards;
 1 1 73 1 2 74 1 4 71
 2 2 75 2 3 67 2 4 72
 3 1 73 3 2 75 3 3 68
 4 1 75 4 3 72 4 4 75 
;

proc glm;
class block trt;
model resp = block trt;
lsmeans trt / pdiff tdiff adjust=bon stderr;
contrast 'a' trt 1 -1 0 0;
estimate 'b' trt 0 0 1 -1;
run;

proc mixed;
class block trt;
model resp=trt / ddfm=kr;
random block;
lsmeans trt / diff adjust=bon;
contrast 'a' trt 1 -1 0 0;
estimate 'b' trt 0 0 1 -1;
run;