Sorry not sure what the exact term is for this question.
I am wanting to highlight a Friday on my daily charts etc with a line on my blank chart so I know that it was Friday's candle. Do i need a indicator or can this be accessed in MT4?
You could try to use an expert adviser for setting an alarm on every Friday, You may have to adjust every Friday manually though. You can download such expert adviser from the internet... as I am not using such I couldn't give you a good example, but just the idea ... :)