Mouse going off window

Hey, i'm trying to make this little paddle mouse controled, and my problem is, the mouse goes off the window to easy, is there any way how i can lock the mouse in the center of the window and still use it to move this paddle around?

heres the code it should work with no media:

;Breakout by Yahfree
;2007-04-4 -> ????-??-(?)?
AppTitle "Breakout by Yahfree","Are you sure?"

HidePointer

;sets the graphics mode, and the setbuffer
Graphics 800,600,32,2
SetBuffer BackBuffer()

;Globalized stuff
Global paddle, paddlex=380, paddley=560
Global ball,ballx=380, bally=580, ballxdir#=0, ballydir=-1, move=1
;Global blope=LoadSound("Beep.wav")

;Constant numbers that never change..
Const ESC=1, RIGHTARR=205, LEFTARR=203, SPACE=57, MOUSE1=1


;Mid handles all of the images and creates a image called paddle.
AutoMidHandle True
   paddle=CreateImage(70,15)
   ball=CreateImage(10,10)

;draws on the empty image container..
SetBuffer ImageBuffer(paddle)
   Rect 0,0,70,15,1
SetBuffer ImageBuffer(ball)
   Oval 0,0,10,10,1
SetBuffer BackBuffer()

;!@!@!@!@!@!@!@!@!@!@!@!@!@!@
;!@!@!@!@ MAIN LOOP !@!@!@!!@
;!@!@!@!@!@!!@!@!@!@!@!@!@!@!
While Not KeyHit(1)
Cls


addplayercontrols()

DrawImage paddle,paddlex,paddley
DrawImage ball,ballx,bally

addcollisions()


;small delay in the loop for less slow down.
;flips, ends the loop and termanates the program..
Delay 5
  Flip
Wend
End

;Include "Functions.bb"

;Player controls
Function addplayercontrols()

;Balls spot if move=1
If move=1 ballx=MouseX()-35
If move=1 And ballx<35 ballx=35
If move=1 bally=paddley-15
If move=1 ballydir=-1 ballxdir=0

;Move=2 if the spacebar is pressed
If KeyHit(SPACE) Or MouseHit(MOUSE1)
   move=2
End If

;Paddle controls
paddlex=MouseX()-35
If paddlex<35 paddlex=35

;calls the moveball function if move=2
If move=2
   moveball()
End If

End Function

;Moving the ball
Function moveball()

bally=bally+ballydir*6
ballx=ballx+ballxdir*6

If bally<0 ballydir=1 ;PlaySound(blope)
If bally>600 move=1 ballydir=-1
If ballx<0 ballxdir=1 ;PlaySound(blope)
If ballx>800 ballxdir=-1 ;PlaySound(blope)

End Function

;All the games collisions..
Function addcollisions()

If ImagesCollide(paddle,paddlex,paddley,0,ball,ballx,bally,0)
ballxdir=(ballx - paddlex)*.025
ballydir=-1
;PlaySound(blope)
End If
End Function

as you can see the mouse can easly run off the screen leavin the player useless untill he gets it back on there, how can i lock it into a place?