I don't understand your question.
If you have Voice Mail service from the telephone company (e.g. Bell Canada or Rogers), callers will be forwarded to your Voice Mail greeting after a predetermined number of rings if you don't answer the call. If you are busy on the phone and you do not have call waiting, callers will be directed straight to Voice Mail. The number of new messages will not affect how calls are processed or sent to voice mail (except if your inbox is full, then a 'mailbox full' message will be played instead of the greeting).
After a caller leaves a message, you will know you have a message waiting for you because any telephone equipped with MWI (message waiting indicator) will start flashing and the screen should display "message waiting" or something to that effect. You will also know you have a message waiting if you pick-up the phone and you hear a 'stutter' tone instead of a normal dialtone. After you listen to your new messages, your dialtone will immediately return to normal and most of your phones should clear their MWI status within a few moments.
You can retrieve your messages by dialing *98 on the Bell/Rogers phone line on which the Voice Mail service is active. You can also access your Voice Mail outside by dialing your own number and then pressing * while you hear your greeting. On Bell you will be asked to identify yourself as a subscriber by re-entering your phone number and password, Rogers should have the same sort of authentication process. I believe both Bell and Rogers have dedicated access numbers you can call to access your Voice Mail remotely without having to dial your own number.
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Side note: Some voice mail systems (although I don't think this applies to Bell/Rogers) have a 'toll saver' feature. This lets you phone your house from a remote location to check for messages and only be charged for the call if you have new messages.
It works like this: If you have new messages it will answer after 3 rings and if you have old messages it will answer after 5 rings for example. In this scenario, you can phone in and if it doesn't answer after 3 rings, you know you have no new messages and you can hang-up before you are charged.