You need to use sprites, cut out the image of say a tree, and stick it in a brand new bmp file, colour the background in black, to make it transparent, then paste it as a sprite,
after you paste your character, then when you move your character up to the tree, your tree will be refreshed on top of your character, making it look like you character is behind the tree.
put a label in your main code, after your move commands (eg if upkey()=1 then xmove =xmove +1) but before your character sprite commands,
call it something like skipmove:
early in your code stuff, you find out what the exact coords of the stump are then you say
if xmove = treestumpcoordsx and ymove = treestumpcoordsy then goto skipmove
then when you walk into the stump your character wont be able to walk past it, so you have to hold the back arrow to make xmove a smaller number, letting you move again, Obviously that code is really messy as i just thought it up in 5 minutes, so you'll probably want to refine it somewhat.
Hope this helps, Ben
Tha D'lithi'om CRR'ist'lls Can'na Tek it Cap'n!