How to modify upload script to accept file type

How do I change this:

[CODE]<?php
$target_path = “uploads/”;

$target_path = $target_path . basename( $_FILES[‘uploadedfile’][‘name’]);

if(move_uploaded_file($_FILES[‘uploadedfile’][‘tmp_name’], $target_path)) {
echo “The file “. basename( $_FILES[‘uploadedfile’][‘name’]).
” has been uploaded”;
} else{
echo “There was an error uploading the file, please try again!”;
}
?>[/CODE]

so that I allow only .doc files and files smaller than 20KB to be uploaded?

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