Look at the API documentation for what ExecuteCommand function requires. It also requires a player object. Also, tostring(Split) isn't how you concatenate a table in Lua. You use table.concat for that.
EDIT:
Also, only functions marked in the documentation as STATIC require that you call the function with a period. Otherwise you can call the function with a colon without itself as the first argument.
EDIT:
Also, only functions marked in the documentation as STATIC require that you call the function with a period. Otherwise you can call the function with a colon without itself as the first argument.