Avoiding Stack Overflow from loops/recursion

This may be a real basic question, so apologies for that but nothing I searched for provided any answers so far...

How can things be set up so that there are two synchonised ways of setting and displaying a value? It's easy, for instance, to have a slider with an associated number object that shows the current value of the slider, or to have a number object graphically represented by an associated slider. What I can't yet figure out is how to set up that number and slider combination so that moving the slider changes the number AND typing into the number object moves the slider.

I realise that this means the objects are fulfilling two separate functions (input and output) but this sort of arrangement is common in the interfaces of other software (dB readout under the faders in Cubase's mixer for example).

Thanks in advance,
JP