Mixing lua-function call and normal script code

["Metzler" <metzler7@...>]

The topic might sound strange, but what i want to do, is the following :
I have a luascript like the following :

function blua()
print("x");
end

running = true;
while running do
print ("s2");
coroutine.yield(1);
end;

My problem is, that i first want the blua function to be executed and then,
anywhen later in my c code i want to start the 'normal' script. Actually,
when trying lua_dofile, he executes the whole file (but he shouldnt). And
with luaL_loadfile it just loads the file and executes the code, but it
doesnt know the blua-function.
So, how could i solve this problem ?
THX for answers