Hiding a Parent form if Child form is opened

If there are 3 forms inside one another and i want to hide the 2nd form on opening of the 3 form but 1st form must be opened.How can i o that?


I am opening form 2 from the main form i.e form 1 and from 3 from form 3.So i want to hide form 2 on opening of form 3 but problem is form 1(main form also gets hide on form 3 opening)
please sort it out.