Is there a way to make a random track playlist play a particular track 1st?

So for instance if you had 500 Rock tracks in a playlist set to random play for two hours,  could you at the start of the playlist firing, play a jingle which says "You are now listening to two hours of rock" Then randomise the rest of the playlist.

Also, on a similar note, is there a way to set an interval playlist to play only during a particular time or whilst another playlist is playing?

For instance you could have a set of Reggae Show jingles but you would only want them played during the reggae show playlist when its playing.

Is any of the above possible? and if so....... how?

Cheers

UKD