Stop User From Uploading Images

[eluser]Vaibhav132[/eluser]
I am working on Uploading image functionality.
The user is allowed to upload only four images.
I am using the following function to count number of images in the directory

Code:

if((count($images) =4)){
echo "You can upload only four images";
}

I am not able to estimate how can i modify and use the function
$this->upload->display_errors(); to stop user from uploading images
after the specific count.

Please let me know, if there is any other way to do this.
Thanx