Customize jQM close button on multiple selectmenu dialog

Customize jQM close button on multiple selectmenu dialog

I am trying to change the close button on a jqm dialog to something other than X. The reason that I want to modify the icon is that the close button leaves the user confused as to whether his selection will be cleared or not (since it is a multiple select). I need to change it to a Done button.  The selectmenu has data-native-menu = "false" and my jqm version is 1.4.2.  I have tried changing the buttonMarkup on pagebeforeshow and on pageinit without success.