Spin object with ease

Hi im very new to flash/actionscript… I have a real problem i hope someone can help with, i would like spin an object in clockwise and anticlockwise direction with ease via press of a button.

tried using,

on (press) {
this.testmovieclip._rotation += 45;

just to get the object to turn… What i wanna do is have 4 buttons, 1st button turns the object 45 degrees, then 2nd button turns it next 45 degrees and so on… and for the life of me i cant work it out!!! Any help would be great.

Have attached .fla of what im trying to achieve.