Pietro, I take it that you have a correctly normalized table design, and you
are using a crosstab query where the dates are Column Headings and the
shifts are row headings.

Crosstab queries summarize the data, so they are never updatable.

It is possible (though not trivial) to design a form that has an unbound
text box where the user can enter a value. You use the Enter event of each
of the other text boxes to copy the value to the unbound box, SetFocus to
it, and set its Left and Width so that it overlies the box that the user
entered. Then in its AfterUpdate event, you write to the appropriate record
in the table (execute an Update, Append, or Delete query statement as
needed), Requery the form (so it hears about the new data), and find your
place again.