Are you talking about a polite farewell, similar to 'Have a nice day!'? You can certainly say 'Have a good week', but not 'work week'. If you want to include 'work' in the sentence, you could say 'Have a good week at work'.

The English do not really say, "Have a good week!" Nor did they tend to say "Have a good day!" It was primarily an American habit. "Have a good week at work!", while grammatically correct, is decidedly un-English. It could be a social faux pas in certain circles. It sounds like a curse. "Goodbye!" is still the most elegant thing to say upon parting.