Modifying Terrain height for editor?

Hi all,
I have an editor I am creating to learn 3d programming, and everything is fine, but I can't seem to get the Terrain to go any higher then just 1 point. Can anyone help me out? :)

Here's my section of code that modifies the terrains height,
it's very basic! :(

Ta.

If(KeyDown(57)) Then
	ModifyTerrain Terrain,EntityX(EdCursor),EntityZ(EdCursor),1,True
EndIf

See very hardcore! - I can't seem to get it to keep raising the terrain, no matter what I put in place of the '1'.

TIA.

Terrain height is always in the range 0.0 to 1.0, although you can
change the way it appears in the 3D world with ScaleEntity.

ahhh cool, thnx

Erm, stuck again. Whenever I load the app and try to edit, it does nothing. Then when I load a previously saved heightmap.bmp and edit the terrain, it raises all of the previously edited sections??

Is there any code that someone could supply to edit ONLY at a desired cursor point (*hint hint*) ;) - I'm new to this 3d-lark and it's rapidly getting on my t*ts. :)

In the Castle sample that comes with Blitz3D you can shoot at the terrain and dig a hole.

It uses ModifyTerrain at the point where the bullet hits.