There are a couple of ways to do this and below is how I would have done it.
Lets say you are showing the score in a textbox. Instead of directly manipulating the textbox objects text propoerty, first I advice to create a global variable named "ShowScore" and tie the timer function to it as you have already done with your current score display system.
Then change textbox objects text property to ShowScore every tick
run once while true
score >= scorelimit1
you can add additional score limits too.
But if by scrolling you mean you have a sprite that has all the possible scores displayed on it and you are scrolling the sprite slowly, you will have to find the distances and make some mathematical function to calculate which score it's showing based on how much it has moved from it's starting position. For that kind of thing, community would need a proejct file to be able to help I think.
Hope this helps.