Background mask for block reference

Hello,
i am trying to add background mask for block reference in single drawing using 'attdef' command for multiple same block's in single drawing not just for selected block (if possible?!).



In 'attdef' window like, I read on this forum, clicking on dots next to Default opens Text Formatting window where i option "A" for background mask where setting up my desire settings for background i get prompt text 'Name' at same insertions point as block and no background mask when click 'Ok' .



Question is what am i doing wrong and how can i change background mask to apply for all same blocks in drawing without duplicate text as show in attachment?


Any help will be appreciate!

Thank you!