[Plugin: More Fields] Override a more fields controlled meta with another plugin

I am trying to create a custom plugin to check and if necessary change a meta field when saving a post

This field is already edited in More Fields so during the edit_post routine the custom plugin change is overwritten immediately after by More Fields with the content that existed in that field previously

Is there a way to keep the meta in More Fields but still change it in another plugin during the edit_post add_action routine?

Thanks

http://wordpress.org/extend/plugins/more-fields/