To save time running a game I thought it might be handy to have a pre-generated list of die rolls to use during encounters. A spreadsheet like Excel seems to be an ideal place to do this, but my knowledge of this type of app is sorely lacking in just how to do this.
This is basically what I do as well.
One thing I find useful is to list your party’s Perception modifiers, use the formula above for a random d20 result for each PC, then add them together (for example, =B2+C2). Then when they walk into a room, hit F9 for an instant whole-party secret Perception roll.