(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?
(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.
Thanks all for recommendation but this activity is not an overhead. Its is task dependent and can be on CP with resource assigned to it.. The tricky part is, it dpendent on the 2 activities above it. So, in simple terms i need to relate it with the earliest start & latest finish of either of the above 2 activities.