utm-redirect.php

<?php
function utm_welcome_redirect() {

	// redirect anyone that is not logged in to /welcome
	if ( !is_user_logged_in() )
	{
		wp_redirect( site_url( '/welcome' ), 303 );
		die;
	}
	else
	{
		// only redirect if user is NOT requesting an admin URL (requires password)
		// and is not at the URL we want them to be at.
		if ( !is_admin() && !empty( $_SERVER['REQUEST_URI'] ) && $_SERVER['REQUEST_URI'] != '/' )
			wp_redirect( get_bloginfo( 'wpurl' ), 303 );
			
		// example to use if you want to simply keep them away from /welcome if logged in
		/*
		$uri = explode( '/', trim( $_SERVER['REQUEST_URI'], '/' ) );
		if ( isset( $uri[0] ) && $uri[0] == 'welcome ')
			wp_redirect( get_bloginfo( 'wpurl' ), 303 );
		*/
		
		die;
	}
}

add_action( 'init', 'utm_welcome_redirect' );