Callbacks, signals and messagebox

[jalkadir gosonic ca]

Hello folks, I have what you might considered a simple one, but my
inexperience with GTK-2.8.0 forces me to ask the most stupid questions,
so, here I go.
In my program, I'd like to have a dialog box that would display text and
an icon.
However, the icon and the text to be displayed will be selectected at
runtime, thus my question is, is there a g_signnal_connect() function, or
any other fuct'n for that matter, that will allow me to pass specific
parameters to a callback function?

Is this possible in GTK-2.8.0?

tia