Control rate of change of a cell using VBA?

Ok, here's one that I really have had no luck searching for...

I'm writing a little sheet to test some navigators on their basic speed/distance/time calculation skills. Ignore the clocks in Row 1, they're unrelated.

What I'd like is to simulate some basic acceleration / deceleration characteristics of a vehicle against a speed demand set point that the user enters. Obviously, no vehicle can go from any speed to another instantaneously, so I'd like my end users to have to take this into account when setting their demand speed.

Simply put, I'd like the actual speed in cell H4 to always target the demand speed in H3 and always return a result, but lag behind the demand speed slightly when changing.

I appreciate this is very basic - vehicles will have individual acceleration curves which are obviously non-linear, and acceleration and deceleration will be different to each other. But, for now, a simple linear control to limit the rate of change cell H4 would be terrific.

Cheers in advance,

Roy K.

Hi there,

First up, thanks very much for your response, much appreciated!

The overall effect of that formula is roughly what I'm trying to achieve. Although it doesn't seem to work at all on deceleration, or when changing to a new target speed after one is reached.

But, yes, I think we're barking up the right tree, maybe!

Deceleration will be done by moving the slider bar to the left to lower the demand speed, or by clicking either the "Stop" or "Crawl" preset speed buttons.

Also, you've used a reference to my H1 cell clock called "Rally Time". This isn't anything to do with the acceleration or speed part of my sheet, that will eventually just display laptop time, activated by opening the worksheet.

Hi Tsjallie - just gave that a whirl and it looks absolutely perfect. I'm trying to get Rally Time to run from Worksheet_Open and reflect laptop time, once that's working I'll integrate your code.

But for now I'm calling this solved.

Very much appreciate the assistance, thank you!