// INPUT =================================
//Sel = clipboardData.getData("Text"); 
Sel = document.selection.Text;
if(Sel.length == 0)  quit();
//Sel = Sel.replace(/(^\s*)|(\s*$)/g, ""); //LTrim/RTrim
//if(Sel.length > 20000) Sel = Sel.substr(0, 20000); //not to many please ;-)
out ="";

// CODE =================================
for(Pos=0,strLen=Sel.length;Pos<strLen;Pos++){
	nASC = Sel.charCodeAt(Pos);

	if(nASC > 64 && nASC < 91){
		nASC = nASC +13;
		if(nASC > 90){nASC -= 26;}
		out += String.fromCharCode(nASC);
	}else if(nASC > 96 && nASC < 123){
		nASC = nASC +13;
		if(nASC > 122){nASC -= 26;}
		out += String.fromCharCode(nASC);
	}else{ 
		out += Sel.charAt(Pos);
	}

}
// OUTPUT =================================
// //Out to an dialog:
// if(Sel.length > 1000) Sel = Sel.substr(0, 1000); //shorten for the dialog box
// if(out.length > 1000) out = out.substr(0, 1000); //   remove for to insert into an document
// alert(Sel + '\n\n' + Sel.length + ' signs ROT13 =>\n\n' + out);

// //Replace clipboard with processed text: 
// clipboardData.setData("Text", out);

//Replace selected text with processed text:
document.selection.Text = out;