Setting up a column of "enum"-fields in Excel
Piece of cake.
1) Enter your list of the fixed values. (These have to be in the same sheet as the cell you want to restrict)
2) Click on the cell you want to restrict. Select "validation" from the Excel "Data" pull down menu
3) In the pull down on the "Settings" tab select "List"
4) click In the box labeled "Source" then select the cells that contain the values set up in step 1)
5) Click OK and you are done.
You can do this for any number of cells
You will see a pull down icon next to the restricted cell(s). Click on it to choose only values in the list. Excel will not allow any other value in this cell.
Look around in the Validation dialog box and you will see you can tweak how this works.
Rather than selecting a buch of cells with the values in them you can write the values in as a semicolon seperated list in the source box instead.
Also the restriction in step one of the first answer "(These have to be in the same sheet as the cell you want to restrict)" is not true.
If fact it is good practive, especially if you have quite a few of this lookup list in use to put them all on a LookUps tab and then hide the tab so that general users cannot see it & fiddle with it.
To get round the restriction mentioned you must set up a Named Range to identify the list of allowed entry items. Because the Named Range is recognised throughout the entire workbook you can then use this name to specificy the list in any other tab you like. In the Source box you type an = sign immediately followed by the name you chose for the Named Range