Query That Adds Data For Every User

Dear Masters;

I have a Messages table; I use this table to post System Messages to my users. But what I don't know is how can I add data for multiple users. I mean I want to add same message for multiple users (ex: Please update your infos). In the belove table I have some messages for users 100 and 200; How can I add same (please update your infos) messages to both users?

Ex: Messages Table

ID    UserID    Msg

1      100         "Hello"

2      100         "Hi"

3      200         "Hello"

 

Thanks..