You can't sync your Windows Outlook calendar
to the Retail Sales calender - if you sync to your PC at work, the Outlook calendar will be a separate calendar on the iPhone. To do that, before connecting the iPhone to the PC, open iTunes Preferences (devices tab) and turn off automatic syncing. When you connect the phone, go through all the tabs and turn off everything except calendar syncing (disable syncing of music, apps, etc.).
Note that a side effect of doing this is that the calendars from your Mac will also sync back to Outlook.
One alternative would be to use something like
O2M to export your Outlook calendar to a .ics file, take that home on a flash drive and import it into iCal (you could then choose to import it into the Retail Sales calendar), then sync your iPhone.