Jųan, There are some quick and dirty things you can try. Place a piece of aluminum window screen in front of the display before mounting it in the enclosure. They make different grades and gages of screen. The rule of thumb is the diagonal dimension of the openings should be the wavelength of your noise divided by 3 or 3 times smaller then the wavelength of intrest. Make sure the screen is grounded to the enclosure. Use this rule of thumb for any openings you might have as they are all places for emisions to escape. Being a amateur radio operator and equipment builder this rule of thumb has come in handy in the past years.

Dave Purola,
N8NTA