urlify should prefix string to url

Hello

I am using urlify, cck and views on a drupal 5 installation.
I use cck to split up blogposts in categories. I have made a couple of views that each show just the blogs of that specific category. I would like urlify to prefix the category to the url.

Current situation:
- i made a text-field called inhoudstype (field_inhoudstype)with cck. Possible values are 'blog', 'work', 'play'. This field is shown when a blogitem is created.
- a user makes a blog, and needs to (obligatory) select either one of the options (radiobuttons) as a value for that field. Lets say he picks 'play'. And writes a post titled: you gotta love tennis.
- urlify automatically add a nice url for the page (well, it just makes a URL-alias) 'you-gotta-love-tennis'.
- the poster needs to prepend 'play/' to the url because my menu depends on the url: the menuitem 'play' is highlighted when a 'play' blog is viewed (in other words when 'play/' is part of the url.
- i use a view that shows teasers of all posts where Text: inhoudstype (field_inhoudstype) equals 'play'

Wish:
I would like to get a URL like this: 'play/you-gotto-love-tennis' automatically, bcs asking the user to add it is both error prone and user unfriendly.

Can anyone build me such a thingy and if so, how much would that cost?
Or is there an other way to get to the same results for which i do not need a new or changed mod? I will pay for any solution that is not error-prone nor user-unfriendly.

Regards
Kimmeehh!