spell work

I'm looking for imput to craft a protection spell for a business, in such a way that it keeps negative energy out without affecting day to day business.  I have a business in a small town, so word of mouth is faster than the telephone, but I have a couple of customers that are rather dark.  My small daughter comes to work with me and it affects her when these people are here.  I would like to either be able to contain their energy in such a way as to not affect my shop, myself and my daughters.  Any ideas would be welcome.  I come from a decidedly  Celtic tradition, but am open to any suggestions.

Blessed Be!