Recalculating fields when foreign value changes

[phil]

I was wondering how I would achieve a recalculation of a field A when a foreign field B, that is part of the calculation, changes, without having to save the dataset around field A.
Let's say field B has the value 25 and changes to 50.
Then I want all fields that have this field in a formula to be recalculated.

[tanya]

It is possible with workflow, Update Related Record action