How do I put a semi transparent layer on my form

I have read some questions about this in the last week or so, on stackoverflow.

My requirement is more or less the same.

I need to put a semi-transparent layer on top my form, but this form may have several other components: Lists, Edits, Labels, Images ,etc

I need this semi-transparent layer to be on top of all that.

The idea is to fade areas of the form that the use those not, or cannot access in that moment.

I use Delphi 2007.

Thanks