Okay, that works. (It didn't work before when I selected multiple records because I didn't follow through. When only one little edit field appeared I just assumed only that record would be edited.
)
Here are some instructions that might be integrated into the appropriate spot in your procedures:
1. Using Ctrl or Shift, select the records you want to change.
2. Move the cursor over the header of the field that contains the values you want to change but do not press any mouse button.
3. Now type F2. A single edit field will appear over one of the records.
4. Type what you want into that field.
5. Type Enter (Return). Whatever you typed in the edit field will automatically appear in that field for all selected records.
And last but not least, it took me a while to understand that the column that gets added during your procedure is not a library field in the database, so it cannot be removed by using any of the Library tools. It seems to only exist in the "view", and as such, one must go to "Customize View" and remove it using that dialog box.