function toggle(id) {

// Create image ID name
var img_id="img_" + id;

// Get main block element
var El=document.getElementById(id);
// ...and image element
var ImgEl=document.getElementById(img_id);

//Toggle the block and image
if ( El.style.display == "block" ) {
    El.style.display = "none";
    ImgEl.src = "/calendar/images/zplssmbl.gif";
    ImgEl.alt = "Show events";
} else {
    El.style.display = "block";
    ImgEl.src = "/calendar/images/zminsmbl.gif";
    ImgEl.alt = "Hide events";
}

}