hey everyone im new to this site and javascript. i really need help coz ill go blind soon for researching

what im trying to accomplish is simple but i couldnt.. i have a set of images with the id 'resizing' its in the middle row of a 3 row table. top and bottom rows have fixed heights.

now i need a script that will calculate the window height and resize the height of images with the id 'resizing' to 70% of window height.. here is what ive written but it doesnt work and i call that function on body onload.. should i call it on img onload once ive got a working script?

function resize_images()
{
var img = document.getElementById('resizing')
var window_height = document.body.clientHeight
var image_height = document.getElementById('resizing').height
if(image_height = window_height / 100 * 70)
{
img.style.height = window_height / 100 * 70
}
else
{
img.style.height = window_height / 100 * 70
}
}