sending data to another site without changing code

Question

sending data to another site without changing code

suppose there is a site A and form of my site is same as in site A.
what i want is that
when i fill the form and submit it the data of my form should fill the form of site A and submitted automatically.

the result will be display in my site

NOTE: i dont have authority to change the code of site A

how can my data accepted by the form of site A

please help
sandy