Sorry, My mistake...
I have looked int he online-help of Access. Here is the result:
"Change font, or font style, size, and color in a datasheet
Open a table, query, form, view, or stored procedure in Datasheet view.
On the Format menu, click Font.
Click the options you want.
For information about a specific item in the dialog box, click the question
mark at the top of the dialog box, and then click the item.
Note Changing the format of a specific datasheet overrides the default
datasheet format defined in the Datasheet tab of the Options dialog box
(Tools menu). "
I thought it will be just enough to select the colmn and change its font.
But that actions changes the font in the entire table.
Maybe MS should answer the question "Is that possible..."