How to get block at coordinates?

[_XxFedexX_]

You can do it with this code:

local blocktype = world:GetBlock(player:GetPosition():addedY(-1));

I get error attempt to index local 'PlayerWorld' (a nil value)
with this code:

33 function testBlock(aPlayer, OldPosition, NewPosition)
34     local PlayerWorld = OldPosition.world -- I get error here
35     local block = PlayerWorld:GetBlock(aPlayer:GetPosition():addedY(-1))[/font]
36 end

And thank you for your support!