In just the last few months, however, almost 7 million consumers have viewed its Pink Glove Dance music video on YouTube.   The charming video shows employees of Providence St. Vincent Medical Center in Portland, OR dancing while wearing Medline's pink gloves. The video cost less than $20,000 to produce.  Its impact on customer and employee relations has been priceless, according to Medline PR Director John Marks.   "Numerous customers (who've seen the video) have written to us saying that they feel great about doing business with us -- that's the ultimate impact you could hope for from any marketing program," he said. Med-Line has no previous experience in consumer marketing and never expected the video to go viral.   The 3:38 spot and pink glove line have been so well received that what was expected to be a seasonal product became a very successful year-round item, said Marks.   One dollar from the sale of each case is donated to the National Breast Cancer Foundation to fund mammograms for women in need.