In a MDI program how to open an exe file in a child?

Question

In a MDI program how to open an exe file in a child? I have made a program which is of MDI, but I want to open exe file in a child rather than child form or MDIParent. As in my coding in program.cs I have written Application.Run(new MDIParent1()); // to open Parent form Or I have written Application.Run(new form()); // to open a form But as I said I want exe file to open whenever I click new on MDIPARENT form, How can I do it? Novice in programming.