Need help with an effect

[KrazyK]

Hi all,
I've started work on another demo remake and my brain has stopped functioning.
I need to code what looks like a simple effect but can't for the life of me figure out how to do it.  I'm sure I did the same effect when i used Stos years ago but converting it to PureBasic has got me stumped.
I've tried a few different methods and failed!

It's a simple pour down effect where a logo drops down in increments to a position below and then pours back up again.
Here's a quick n dirty animation from the demo in question.
It's the last thing I have to do for this remake and will of course credit anyone who can help !

[edit]
I think i've finally worked it out during a Eureka moment! 
I've even preshifted the sprites now so it's easier to use.

[aNdy]

From your animation, it looks like each letter is divided horizontally into "zones", for example, then each zone is stretched in turn to simulate "pouring" as you put it.

Saw similar on the Amiga back in the day, except it seemed to pour a scanline at a time.

How did you do this in the end? In code and build sprites on the fly or pre-render then display sprites? I'd have cheated and drew the letters as animating sprites...