Movement via actionscript problem

i have this code to move a clip from point a to point b. it works fine, no problems at all with the movement. the problem i am having is to stipulate what point a is. the code lets me predefine what point b will be. i can state what the x and y coords will be for that but i cannot say what the point a x and y coords wil be

a step by step to movement is below:

add code to the movieclip

onClipEvent(load)
frict = .2
ratio = .1
turnSp = xSp = ySp = xScSp = yScSp = 0
turnEnd = _parent.turnEnd
xEnd = _parent.xEnd
yEnd = _parent.yEnd
xscaleEnd = _parent.xscaleEnd
yscaleEnd = _parent.yscaleEnd

onClipEvent(enterFrame)
turnSp = turnSp*frict+(turnEnd-_rotation)ratio
xSp = xSp
frict+(xEnd-_x)ratio
ySp = ySp
frict+(yEnd-_y)ratio
xScSp = xScSp
frict+(xscaleEnd-_xscale)ratio
yScSp = yScSp
frict+(yscaleEnd-_yscale)*ratio
this._x += xSp
this._y += ySp
this._rotation += turnSp
this._xscale += xScSp
this._yscale += yScSp

now set the parameters for the tween on the main timeline
( on a frame or button action )

xEnd=475
yEnd=300
turnEnd=180
xscaleEnd = 120
yscaleEnd = 200

see the problem?

i dont. would love a little help on this please!