Rebound object of edge of screen?

I have a routine to move an object (all 2D).
Sample below.

I need to test for player moving off edge of screen (or any given boudary),simple enough normally - But I want the player to bounce off the edge of screen (screen edge being angle of incidence) with the same speed/friction etc as the player collided with screen edge.
Hope this makes sense to someone

Thanks in advance.
ps.I`m not sure how to add code correctly so I have cut/paste.

;ACCELERATION (PLAYER ACCEL) ADDED TO SPEED VECTOR (DELTA_X#)
If playerdirection_u = 1 ;FLAG FOR FORWARD

delta_x# = delta_x# + Cos( player_turnangle#) * player_accel# ;PLAYER_TURNANGLE

delta_y# = delta_y# + Sin( player_turnangle#) * player_accel# ;IS PLAYER DIRECTION

EndIf

;CALCULATE TRUE LENGTH OF SPEED VECTOR (PYTHAG`)
speedvectorlength# = Sqr( delta_x# * delta_x# + delta_y# * delta_y#)

;IF MOVING THEN DECREASE SPEED BY FRICTION
If speedvectorlength# > 0

delta_x# = delta_x# - (delta_x# / speedvectorlength#) * player_move_friction#
delta_y# = delta_y# - (delta_y# / speedvectorlength#) * player_move_friction#

EndIf

;IF WE ARE GOING TO FAST THEN REDUCE SPEED TO THE MAXIMUM SPEED
If speedvectorlength# > player_max_speed#

delta_x# = delta_x# + (delta_x# / speedvectorlength#) * (player_max_speed# - speedvectorlength#)
delta_y# = delta_y# + (delta_y# / speedvectorlength#) * (player_max_speed# - speedvectorlength#)

EndIf

;UPDATE PLAYERS COORDS
player_x# = player_x# + delta_x#
player_y# = player_y# + delta_y#

A simple version. To add code use ...

{code}
My code goes here
{/code}

But change the {} for []

Stevie

global GW = graphicswidth()
global GH = graphicsheight()

[your code]

[before update player coords ]

CheckX# = PlayerX + delta_x
CheckY# = PlayerY + delay_y

if CheckX < 0 or CheckX > GW delta_x = - delta_x
if CheckY < 0 or CheckY > GH delta_y = - delta_y

Thanks for that Steve.....works a treat!

....... the code looks so simple as well.