Fall-back cursor theme?

Hi,

I'm using a very nice cursor theme with one drawback: it doesn't have a full range of cursors, meaning that cursors not available in the theme are substituted with the default X cursors which I don't like. Is there a way to tell Xfce which cursor theme to use should a particular cursor be missing from the set theme?

While I'd like to do this mainly for Xfce (my default and most used GUI) I would also like to be able to set cursors and fall-back cursors on other GUIs as well. In particular AfterStep, LXDE, FVWM-Crystal and OpenBox. Right now I'm using gCursor for for the secondary GUIs and Xfce's Settings Manager for Xfce, but neither has a way to specify fall-back cursors.

Thank you.