Scripting, setting fields to value list

[atownart]

I am wanting to set a value list to a field on a object exit when selecting another. A small example scrtipt would be really appreciated.

This needs to happen on the fly as the value lists could be one of many depending on the value selected.

This can not be done via relationship driven conditional value lists.

If this is not possible I think it may involve changing layouts dependant on the value selected.