This is one of those "If you have to ask its beyond your capabilities" questions. What you want to do is possible, but you really need experience with a lot of aspects of Access to achieve it. How good are you at VBA?
My first suggestion is to really consider if this is necessary. What do you think this is going to help you achieve and is that really true? You are essentially adding a confirmation step to the input process and nobody pays attention to those. Especially if that confirmation step is always part of the input process, people are going to input their data and automatically click that "Save" button no matter what without thinking it through because that's what they train themselves to do.
Think of a web page that has a popup that you must click through to "Accept All Cookes"--nobody realy pays attention to them, they just click to get that damn popup out of the way. That is what you will be creating with this "Save" functio---a mindless click event users automatically go thru.
Now, if you still want to do this then google "Unbound Form Access" the first 3 results I found where all very helpful in achieving that type of system.