I'm not quite sure on how this works, but I think there's a setDatablock function, and a schedule/delay type thing.
Try something like this:
function Syringe_changeData(%player)
{
%player.oldDatablock = %player.datablock;
%player.newDatablock = (Desired datablock);
%player.setDatablock(%player.newDatablock);
%player.revertData = %player.schedule(5000,"Syring_revertData);
}
function Syringe_revertData(%player)
{
%player.newDatablock = %player.oldDatablock;
%player.setDatablock(%player.newDatablock);
}
Again, I wouldn't really call myself a scripter, but this should help you get started. If it doesn't work, don't be surprised.