A ScrollBox without scrollbars

I want use a ScrollBox, put a large image in it, and manage the scrollBox with MY scrollbars, not the Horiz. and Vert. scrollbars which can be 'attached' with the scrollbox.
If i put the Visible propriety of the Horiz and vert. scrollbars to false, yes they disapear but i cannot more scroll the scrollbox.
What i want is :
Horizscrollbar.range:=x (x > scrollbox.width)
Horizscrollbar.visible:=false
Vertscrollbar.range:=y (y>scrollbox.height)
Vertscrollbar.visible:=false

The Horiz and vert. scrollbars are 'ENABLED' (ie i can change their   Horizscrollbar.position and Vertiscrollbar.position) but they are not visible on the screen.

Any idea ?

TIA

jm Verdi