How to update certain occurance of certain text using sed command?

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http://stackoverflow.com – As Per my automation requirement, I need to execute below mentioned xml request with different values. As per during first round of execution should be performed with the different values lies within first occurance of startDate, and so on. I know this can be done using programming in awk or some sort of shell commands. but I am much interested if we can solve this using sed command. Please suggest your solutions using sed command. Thanks, Priyank Shah -----------------------------------------Test.xml----------------------------------------- <Abc> <dateRang (HowTos)