Change model by defined parameters

[mitterlehner.c]

Hey Guys,

after strolling through several blogs and videos, I can still not find any ideal solution for my issue.
I made a model of a window and i want its measurement to be adjustable, when I merge it to a new scene.

Sure, I could put an edit-poly-modifier on the group, but this solution does not seem professional to me.
Also, scaling is not possible, because this would also scale the width of the frame, and this one has always to be the same. 

The screenshot is showing a model i purchased and this one works really well. But I have absolutely no plan how I can turn my finished model into a box ... 

[oliver]

It's the other way around: you start with a box and model it that way, that changing the box' parameters changes the dimensions but not the modeling ontop.
Example: create a box, apply an EditPoly-modifier and inset one side by 2cm. Changing the box' size-parameters will not change the inset-value, it will stay 2cm. If you use e.g. "Connect" to insert edges, these will get changed.
So it's a matter of the tools you use to model in order to keep the modeled appearance or not.