How to make dependent one form to another one's result

Hi All,

while customizing I am facing one issue.

I have done one customization where i am using two forms. But my parent form I would like to monitor on the basis of result of child form as follows.

My parent form is Packing slip and my child form is also a packing slip.

but what I want, is to post parent packing slip form on the basis of posting of child packing slip form. means if child packing slip form is posted then only parent packing slip form should be posted. how we can add this into our code.