how can i calibrate servos??

i use tower pro mg995 servos but angles are not accurate. i send angles via matlab (with servo.Write()) but the angles are not exactly correct. these servo works with specific pulses and goes in specific angles ,for example if you send 1500us servo goes in 90 degrees (with servoWriteMicroseconds command) but only if i use arduino only. in matlab does not exist this command that sends specific pulses. i have donwload adiosrv and arduino contents but there is not exist these command(servowritemicroseconds). does anyone knows how to send specific pulses via matlab on servos?