I don't believe this is possible out of the box, though you may be able to use some Javascript to achieve the desired functionality. However, what I would recommend is to create a custom table in the elasticube (rather than a custom column, if you do not want to muddy the perception of the prod database tables). In your custom column, you can extract only the id of records which match the conditions (less than 32 characters in length), create a relationship from the custom table to the primary table on "id", then use the id field from the custom table to apply a filter to the widget that you want to affect.
