Passinga data trhought forms

I have anothr little question....
I have an MDI parent, and 2 mdi child
the parent is always enabled, the first child disable itaself and call the second child, who get the control...

I have a problem to passing data throught the second child to the first child. When i close the parent with the 2 child open, the application says that is an error.
To remain open the sencond child I have do a loop, and when exit the loop the 1 chil get the control, with the data that the 2 child have send him....
Is the best way to do this?
There is a best method?
Thanks to all
Sorry for ugly english...