Setting up excel for online viewing/editing by multiple users

What I have is a football selection workbook. 1 sheet represents one week of games for that week. I have close to 100 players and currently enter the data using the copy/paste special function when the players make their selections in an online message board forum. What I would like to do is allow users to enter their own game picks but restrict their access to view the games we are picking from and their username column to enter their picks on their own. I'm think I'll have to assign passwords to all users to make this happen, but after doing some research online, I can't figure out if this is even possible or how to make it happen. Any ideas will help.

Check out my sample below. I want all users to see the Range of B4-23 and C4-C23 and E4-E23. Then I want the specific user to have access to his cell range to enter their own selections but NOT be able to edit anything other than their own column range, For example, the first player: 19au48, I want him to only be able to edit the cell range of G4-G23. The users selection cells are the same every week, but there are different sheets in the workbook for each week of the season.

Is what I'm wanting to do here even possible and if so how complicated is it to set up?

A couple of questions, for clarification purposes.

Will all 100 players have access to the same file? By this I mean one file on one computer/network?
If so, how do you plan on dealing with file access conflicts?

BSB

Well, that poses another issue that I hadn't considered. Obviously I would need the ability to have more than 1 person have access to the sheet at one time.
This may not be doable. Multiple people accessing the sheet is not something I considered.