What should column 3 return?

You could try

var result  = @DbLookup( dbname,  "vFreeL2", "Barbariga pri Puli\\št. 098008", 3);

Then print or alert result to firstly see what you have and also print or alert typeof result to see what data type is being returned.

Also, how are you setting dbname? The problem may lie there. Should be something like:

var dbname= new Array(database.getServer(),database.getFilePath());