Append file-size to links

Hey there all

I have a custom file manager attached to my CKEditor install. I can make the asset manager return a string containing the selected file's filesize to the link dialog. However I have no idea how to append that string to the end of a constructed link. It can't be a part of the link, it just needs to be text, ie:

My File (300kb)

Any ideas how I can achieve this?