Hi, 

I have a webshop where i sell engraved signs.

I want my customers to be able to write width and height and then the background image is updated/scaled in the designer automatically and the price is updated according to square cm.

Is this even possible?

I have Fancy product and MSPD

You can get the prices according to customers' written width and height. Please explore these options in FPD settings > Addons >  Dynamic Views.