The datasheet view will not allow "per field" formatting as it were. You format the entire thing and that's it. There are numerous options around it, but none are built-in and it will depend on what other software you have. (DataGrid and FlexGrid come to mind.)
Some alternatives are free, while others want usually a pretty small price ($50 or less). However, you would want to make sure that if you purchase such a control, you get a royalty-free license and that the control can embed itself into the DB. Otherwise, all your users have to have that same control.
Google for MS Access RTF DataGrid and you'll see what I mean about all sorts of available options.
