Return values from php to child flash movie

Hello!

I have problem to get return value from post variables.
I have this stucture:
main movie -> preloader
child movie -> animation with contact form (I sending by php mail function)
in playing only child movies everything work ok, but when I load this from preloader than not

in preloader I use loader with "lock root" option
in child movie I have acript with roules to variables:
root.loadVariables (root.urlstring,"POST");

I think that value from php go to the main movie root (preloader) not to the child movie root
Have You any idea how to declare variables to get values from post php to the child movies?