I needed to remove a key from a return delimited list of keys and came up with this formula. I also went ahead and made a custom function that is in this sample file.
$text = example::original ;
$key = example::key_to_remove ;
$text_length = Length ( $text ) ;
$key_length = Length ($key) ;
$key_position = Position ( $text; $key; 1; 1 )
Left ( $text ; $key_position – 1 ) & Right ( $text ; $text_length – $key_position – $key_length )