Zoom in the Camera Boom with a pressed button

Hello everyone, first of all, excuse my English
I’m trying to make the boom of a character’s camera come up softly by holding down a button and move away by pressing another, so far I can get it to vary the distance of the boom but only for a certain value, not incrementally .
I thank you for your help.

Here’s an example of zooming in and out when holding the right click mouse button, when holding you zoom in softly, and when you release it you zoom back softly, my Spring arm length is 300, the MinLengh=100 and MaxLength=300 go ahead and try it out and let me know if you need help with a specific example.
You could do this in a timer if you want.
Increase Interp speed to speed things up a bit.

Thanks for your answer, had tried a similar solution but finally I did it with a timeline and it works well although I do not know if it would take more hardware resources.

Using a timer is generally a good thing in your case here it’s the best solution and for this simple task you don’t have to worry about hardware resources you won’t notice any difference.