I am customizing a screen and have a grid where I would like to specify "Editing takes place directly in the grid".  However the radio button on the grid wizard (Step 5 of 9 Allow Edit) is not selectable.  It is set to "Do not allow..." and the other radio option is disabled and not selectable.
| Do not allow editing of rows | 
| Editing takes place directly in the grid | 
I've done this on many other screens and never had problems setting this option.  I am wondering if there are situations where this is not allowed?  The table I want to allow editing directly is "Vehicle Mileage" table.  Is there a restriction?
Thanks in advance for any help/suggestions. 
Regards, 
Pam