the simplest approach is to use the Change Int32 Effect. With this effect you configure an animation to 'animate' an int32 value. You can configure the start, the end value, the duration of the animation and how often it should repeat. If you want the effect to animate forth & back, you can configure the effect to be symmetric. For example, following parameters configure an effect to run endless in range 1 .. 100, forth and back. One animation cycle (forth <-> back) take 1000 ms:
Now you connect the effect with the Gauge's property CurrentValue. For this purpose, click on the triangle icon right to the Outlet property of the effect and select the property CurrentValue of the gauge object. For example:
The effect will control now the referred property.
I hope it helps you further.