You can make your form model (blocking) quite easily by placing a transparent div at a Z-index "above" the form, the making everything on the form un-clickable whilst that div is present.
this.blockingObj = document.createElement("DIV");
document.body.appendChild(this.blockingObj);
this.blockingObj.style.background = "transparent";
this.blockingObj.style.zIndex = this.obj.style.zIndex - 1;
this.blockingObj.style.width = document.documentElement.clientWidth + "px";
this.blockingObj.style.height = document.documentElement.clientHeight + "px";
this.blockingObj.style.position = "relative";
this.blockingObj.style.left = "0px";
this.blockingObj.style.top = "0px";
Of course you need to remove this.blockingObj when you want to re-enable the form.