Any Revit user will tell you that this isn't possible, at least not easily or out-of-the-box. That is...to indicate which sheet number this sheet is relative to the total number of sheets.
Some firms don't bother with this, others insist and numerous oversight/regulatory organization as well as clients demand it. As a practical matter it just helps the person reading a set of drawings determine if they have the entire set or not, or if they are in the correct order. If they are looking at sheet 25 of 50 and they only have 5 sheets in front of them, clearly there is a problem. Their other option is to check the Sheet Index...assuming they have one.
Now that I've gotten you depressed that it isn't possible I can cheer you up a bit. Phillip Miller with Kiwi Codes is working on a solution that he started out sharing at AUGI. His single license version will set you back $5 USD and a site license will cost you $20 USD. Methinks that sales might be brisk from certain companies faced with meeting this requirement. Phillip has provided a video for you to consider it prior to purchase. They also have other, though New Zealand specific, tools for Revit.
Check it out!