Sorry but you cannot refer to another task's data (predecessor) in custom fields. The only method to refer to other tasks is through code. (VBA for example).



Regarding two scenarios you can compare two versions of the same project. You can Save AS a different file name, change the data as needed and then compare.

Another alternative is to save the scenarios as interim plans and then use the Multiple Baselines Gantt to visually compare the results.

Brilliant, the compare file function does exactly what i need.
Many thanks for your help.