datepicker icon called via default

datepicker icon called via default

I have called a calendar icon file from a script on the form - this works except IE, where I get the "x" for image.  I prefer to call it from the widget defaults.

I have downloaded the themeroller version, including datepicker. The defaults regarding button image that came with the download are:

buttonText:"",buttonImage:"",buttonImageOnly:false,

I wish to change it to:

buttonText:"calendar",buttonImage:"",buttonImageOnly:true,

Note the missing button image from the icons png that comes with the download. I can see that other widgets use those and that there is a calendar icon, but how do I go about calling that supplied icon calendar onto the page by using "buttonimage:"" "?  I suspect there may be more to it...but cannot follow it through.

As a fallback I can put the script back on the form, but why does IE image fail?

Thanks,
Chrissy