Thanks NextDesign,
Sorry but making the expression is not gonna bother me so much.

I have to make 20 separate animations of 15 seconds
1. from 3.59.50 to 4.00.05
2. from 4.59.50 to 5.00.05
... till
20. from 23.59.50 to 00.00.05

My question is more: there is a better way then creating multiple numbers and then having to switch visibilities?
The thing is: I can't set key on my text value: https://dl.dropbox.com/u/1803715/Text%20History.jpg