changing a QTextEdit from a dll

I want to write a dll using QT library
that can control and manupulate the caller executable QT controls.

for example I wantto change backcolor of QTMainForm's textedit1 (which is inside executable).
but this code in a dll that is loaded by executable that has a QTForm.
(dll has no QT Control objects.Just modifier functions that can loaded by other executable)

(thanks before for any answers)

For creating plugins with Qt, you can check http://doc.qt.nokia.com/4.6/plugins-howto.html or Plug & Paint example, which extends an application with plugins.
In order to be able to change a widget from a plugin, you will have to call the functions passing either your widget as parameter, or another instance of object through which you can obtain instances of your widgets.

Regards,
Jancsi Farkas