Thanks to Nut for what is already promising to be a very interesting thread.
After scouring FF for a suitable indie, I have found the attached MT5 ROI Alert. It allows time frame to be set (10,080 as Nut outlined earlier).
I am not that excited about the line style (asterisks) but when I change the line style input the change does not persist. Perhaps those more technical-minded might be able to figure out a way to do this or even offer up an alternative indie.
I guess since this is a weekly hi/lo line that is to be visible on the 1H, drawing the line manually would not be too onerous.
Looking forward to participating in the weeks ahead.