Template question-->editable regions w*h

Hi,

Can anyone tell me how to give a editable region a fixed height en
width.
The regions i create can be expanded to the users wish and i want some
regions to be fixed.

And is there a way to let the user put in a image in a editable region
but still crop the image to the properties i want for instance my user
puts in a image which is 1000*1500 and i want it to be 100*150.

regards,
matthijs