Greetings Lucille,
Try to create an Equipment User Status Profile in OIBS with a User Status such as BDEL "Block deletion" and make that status Set when the status ESTO is set (I'm unable to name the relevant business transaction without looking it up,but there is bound to be one if there is a System Status, I think...)
Then for the User Status make the business transactions mentioned by Forbidden.
- INAK - Set object inactive
- INAZ - Reset object inactive
- LVMS - Mark for deletion
- LVMZ - Remove deletion flag
The idea being to set & unset BDEL whenever ESTO is set / unset. Then BDEL becomes your transaction control for setting the Inactivity or Deletion Flags.
Another way of doing this,and one that should not be mentioned in good company, is using the t-code BS22 to edit the System Status ESTO itself, but I would advise against making changes to a System Status, this can mess up your system badly...