Staying at the Sheraton Wall Centre with a car gives you many options.
I can't give you any solid recommendations but can make some suggestions.
First, try scanning through the "Vancouver Massage" and even the "Vancouver Escorts" sections of eforum.xxx over the last few months. If you click on "Search" on the toolbar at the top of the menu and click on "Advanced Search" on the drop down menu, you can search terms and limit the search to the Vancouver Review section to limit extraneous results. For terms under 3 letters (e.g. "BEX", use the "*" as a wildcard for "BEX*" or "*BEX").
Unfortunately, I can't give specific recommendations as I usually stick to independents with only the odd foray into agencies (when no indies are available).
However, since not many others are jumping in to help you here's a couple suggestions for massage parlours that are fairly close to your hotel (you'll find many more in the Vancouver Massage Section of eforum.xxx).
All of the following have some fairly nice Asian attendants. In Vancouver, it's hard to find any place that doesn't have Asian MPAs so you're in luck if that's what you're looking for.
All of the following places offer everything from a rub and tug to FS. They're more expensive and probably offer less service than some of the Asian micros reviewed on eforum.xxx but are a fairly safe bet for a visitor who doesn't know his way around Vancouver. Addresses and other details for the following can all be found on eforum.xxx or easily through the internet (or PM me):
Broadway Body Care (or "BBC")
BEX
Prosper City (a little further away)
"Higher Priced" and within easy walking distance of your hotel:
Madame Cleo's
Platinum Club
"Higher Priced", within easy walking distance of your hotel, and with perhaps the nicest facilities:
Swedish Touch
From what I've heard, the facilities at Lavanda aren't as nice as those in the above places. I've also heard noise transmission between rooms is not that great at some of these places (notably Lavanda and BBC).
I caution you to do some research of the Massage Section using the "Search" facility to confirm which appeals most to you in terms of price, service and selection. Also, trying to "book" a specific girl days in advance and being confident she will be available at the time scheduled isn't all that certain so you should always have a backup plan (or two!).
Frankly, other than massaging a certain "muscle", most massage parlours aren't very good at massages. So if you're looking for anything more than a rub and tug you might want to consider one of the reputable escorts reviewed favourably on eforum.xxx. Many offer both incall and outcall in the downtown area.
Sorry that I can't be more specific, but at least it's a start for you.