[xmonad] Moving windows to the workspace of their parent window

I'd like to write a managehook that shifts windows to the workspace of their parent, without having to restrict that workspace (ie, without predefining a specific workspace for these windows). For example if I run skype on one workspace, when I get a call and answer it, I'd like the call window to automatically shift to the same workspace as skype. How would I go about this? -- Mina Nagy Zaki