Modifying DM rolls with result still viewable

I'm new to Roll20 and macros, so pardon me if this has been covered before. I know how I can hide my rolls from players. But I would like the option to modify an attack roll while still letting players see the result. For example, an NPC is trying to hit a player, but the NPC's roll is modified by something I don't want the players to know about. So in this example, I'd roll a d20 with -4 modifier ( d20 -4 result 10) but I'd only want the players to see that I roll a d20 and 10 is the result. Furthermore, I would really like a macro that does this without going to zero or negative, so if the roll was at -4 a roll of 1 - 4 would still be just 1. Am I deluded or can macros do this sort of thing?

Most players do not like this sort of fudging, just fyi... ... and no, this is not something you can do with macros w/o players knowing.

What if there is a condition that is unknown to the players, and you need to keep it that way for role-playing purposes, that affects the rolls of NPCs? Any suggestions? For instance, something that looks like an orc is attacking them, but in fact it's affected by an illusory spell and is another creature entirely, with a different attack modifier. How would you handle that?

If you use inline rolls most players are not going to scroll over the box and worry about the math. But if you think this is a valid common situation in your games, just start making all your rolls GM only hidden rolls. If a player ever asked why orc 1 added +5 to an attack but orc 2 added +9, I would just say because and that is good enough because I am the DM.

As stated, this is not available. Closing this thread to stave off arguments for and against fudging.