Some things you can try:
If you start entering data in B2, hit <Tab> to move right each time.
When you come to the end of the set (E2), hit <Enter>, and the focus moves
to C2 automatically (cell under the first cell you used <Tab> on).
OR
You could click and drag and create a selected range, where the first cell
of data entry has the focus (colored white).
Now, hold down the <Enter> key, and you'll see that the focus moves down and
to the right, but *remains* within the selection.
Hold <Tab>, and the focus moves right and then down, remaining within the
selection.
OR
Select a cell, hold <Ctrl>, and click in other non-adjacent cells, making a
non-contiguous range.
Hitting <Enter> or <Tab> will now move the focus to each cell, in the
*order* that you selected them.
In fact, you can name and save these selections to be used for filling
forms.
Check out this old post about these "named ranges".
http://tinyurl.com/39vzv
Another option is to unlock the cells that you wish to accept data entry,
and then protect the sheet.
When you hit <Tab> on a protected sheet, the focus will move from
unprotected cell to unprotected cell.