Add black head and tail on WMV

Hello to you!

I do a lot of Quicktime-rendering from After Effects.

From this QT-file I always do a compressed wmv-file to email the costumers.

What I would like is to add one second of black in head and tail onto the wmv-movie.

Is there an app that lets you do that? I've tried Adobe Media Encoder, Sorensen and older versions of Canopus.

Any other techniques?

What I most often do now is to import the qt-movie into After Effects and add the extra seconds in a new comp and render it as a wmv, but it would be great to be able to do that automatically.

Thanks!