Setting marker zIndex in IE

I'm trying to set zIndex to markers, mainly, i want to set all green markers on top.

The code below works GREAT in any other browser but IE!

I'm checking in the marker is green if it's containing 'st1' in the filename.

I'm using mootools so the code is a bit mootools specific, but any Javascript help would be appreciated:

gmarkers.each(function(mrk,ind){
    try {
        if (mrk.qa.image.indexOf('st1')!=-1){
            if (Browser.Engine.trident){
                mrk.Ir[0].zIndex = ind + 1000
            } else {
                mrk.Ir[0].setStyle('z-index',ind + 1000)
            }
        } else {
            if (Browser.Engine.trident){
        开发者_如何转开发        mrk.Ir[0].zIndex = ind
            } else {
                mrk.Ir[0].setStyle('z-index',ind )
            }

        }
    } catch (err){}
})

found it, it's mrk.Ir[0].style.zIndex, not mrk.Ir[0].zIndex