AS3 : XML Into Array Login Form Details

i want to make a login form in as3.i have two input text fields(usrname , password )  and one submit button on stage.

when user inputs those fields and hit submit i want the flash to load the all available usernames and password into an array and check if the input details match to any of the imported details of xml into array. if it matches it traces welcome otherwise invalid input.

how to do it ?

pls help asap