calling form in dll from function in dll


Not sure if this is the right group but try it anyway.

I have a dll with an exported function that is called by a service running
on NT4.
In that DLL I need to do some graphic manipulation so I need a canvas/form
etc. These are hidden since output will only be to file.
What I want to know is if it is at all possible to do this when the function
is called from a NT service ?
If so how do I call the form functions from the exported funtion in the dll
? that is how do I create the form.
So I have a library with a export function. the library has a form unit
included in the uses clause of the library. The exported funtion needs to
call the form function (cannot be done from the service !)

Any help and/or excamples would be welcome.