How to stop a movie clip moving

Question

I'm not newbie to flash but I am newbie to coding using
actionscript!!!
I am trying to create a button that moves a movie clip
("content1") diagonally across the screen but once the movie clip
reaches a certain x co-ordinate I want it to stop and then when I
click another button I would like it to return to it's starting
position. At the moment the movie clip moves if I click one of the
buttons but as soon as I click another one it stops which it
shouldn't it should go back in the other direction. The other
problem is that once I've clicked a button I cant seem to get it to
stop moving once it reaches a certain _x position it just keeps on
moving off the stage.
Below is the script I have so far not including any
conditions to check if "content1" has reached it _x position
Could anyone help please!!!!
//on Right movie clip containing the button
onClipEvent (enterFrame) {
_root.content1._x += speedX;
_root.content1._y -= speedY;
//on Right button inside movie clip
on (press) {
speedX = 5.5;
speedY = 1.33;
//on Left movie clip containing the button
onClipEvent (enterFrame) {
_root.content1._x += speedX;
_root.content1._y -= speedY;
//on Left button inside movie clip
on (press) {
speedX = 5.5;
speedY = 1.33;

Answer 1

Many thanks ClBeech!!!
I've tried the code you suggested but it doesn't seem to work
:0(
I'm working on a Mac using Flash Pro 8 which only has the
option to publish as 'actionscript 1.0 or 2.0' is the script you
supplied an actionscript 3.0?
Below is the script with the amendments, I've changed my
button instance names to match the script you supplied (left_btn /
right_btn)
stop();
import mx.transitions.Tween;
import mx.transitions.easing.Strong;
var rposX = 369;
//the ending x of the right position
var rposY = 84;
//the ending y of the right position
var lposX = 116;
//the ending x of the left position
var lposY = 154;
//the ending y of the left position
right_btn.onPress = function() {
new Tween(content1, '_x', Strong.easeOut, content1._x,
rposX, time, false);
new Tween(content1, '_y', Strong.easeOut, content1._y,
rposY, time, false);
left_btn.onPress = function() {
new Tween(content1, '_x', Strong.easeOut, content1._x,
lposX, time, false);
new Tween(content1, '_y', Strong.easeOut, content1._y,
lposY, time, false);