When should to package DLL

[Wong]

For a certainty, there are many benefits to use DLL. It can divide each functions.
Often I use callback function to communicate with class.But it's unhandy, because member function can't be callback function.

So, i would like to hear the views of members. When should to package DLL, or shouldn't.
Did you often use callback function?

Although often use callback function, I don't like it

Added after 5 minutes:

Sometime i feel need not to use dll, But boss don't think so

[nish]

Last time i checked. Qt solves callbacks by signal-slots. Your post is very unclear. try to rephrase your question.