Think-time functions are PeopleCode functions that suspend PeopleSoft processing to wait for an external event (user input, an external process to complete etc). PeopleBooks strongly recommends not using think-time functions in certain PeopleCode events.
However, what category does MessageBox fall into? Well according to PeopleBooks:
If the style parameter specifies more than one button, the function behaves as a think-time function and is subject to the same restrictions as other think-time functions.
In other words, MessageBox is not a think time function when the style parameter only specifies one button! This can only be the case when the style parameter is 0 or %MsgStyle_OK which means only show the OK button. So if you use 0 or %MsgStyle_OK as the style parameter, you can use MessageBox as a normal function in any relevant PeopleCode event.
