Getting from St. Lucia to Tortola is going to be neither "cheap" nor quick - it could take you "all

We are going to St. Lucia in January for a week then on to Tortola. I am trying to find the best (cheapest) way to accomplish this. I know there is a ferry that runs between Tortola and St. Thomas. Please help.
Getting from St. Lucia to Tortola is going to be neither "cheap" nor quick - it could take you "all day". It will most likely entail two or three connecting flights and cost somewhere between $350US and $400US per person. You'll either have to connect through Barbados and/or Antigua or have make your way back to San Juan and then fly to Tortola. Check flights on Liat Airline ( www.liatairline.com ). American Eagle used to fly between St. Lucia and San Juan but recently they've cut back drastically on their San juan operations and I believe they may have ceased flying to/from St. Lucia - you'll have to check with them to be sure. You may find the same logistical difficulties flying into St. Thomas - again check Liat Airlines.
From St Lucia you can take the catamaran L'Express des Iles to Dominica or Martinique (or fly), then from Dominica or Martinique fly to Antigua southwest airlines vacation packages and from ANU to Tortola. Making southwest airlines vacation packages all those connections work will be a challenge, St Lucia and Tortola are not islands I would think of as natural pairing for a trip.