Getting LUA error msg

Anyone know how to get an error message from LUA?

I'm not calling any functions from LUA, I'm simply running a LUA script via lua_dofile(LuaState, "test.lua") and nothing really happens if there's a syntax error or something, I'd like to print LUA errors but can't figure out how to actually GET the error messages from LUA.

If luaL_dofile(luastate,"test.lua")
Print "[ERROR] "+lua_tostring(luastate,-1)
EndIf

Well... *cough* that was easy, heh.
Thanks for the straight forward answer mate. :]

It returns true when an error occurred? Are you sure?

It returns the whole error message, it works perfectly.

Yes. If there were no errors, it returns 0.

That doesn't make sense at all...

Yes it does.

If an error occurred, luaL_dofile() returns True.
If there were no errors, luaL_dofile() returns False.

http://pgl.yoyo.org/luai/i/luaL_dofile

It makes more sense to say

If Not luaL_dofile(luaState, "test.lua")
'Error occurred
End If

Imo the current way is reversed logic...

Does any of you know how to store a LUA function in my field?
I've tried to use lua_tocfunction() but can't get it to really work...
What I basically want to do is have a button in BlitzMax as the type Gadget with a field called Func() and then in LUA do something like

function Clicked()
print("Hey!")
end

gadgetfunction(Clicked)

Which would set my Func() field into the LUA function Clicked(), then when I click the button just call Func()

I guess what I'm asking is... how do I pass a function as a parameter in LUA?