PROBLEM wysiwyg editor

Hi, I try write function for put class definiton in <P> tag in wysiwyg editor. I have problem because I use execCommand method which hasn't command for insert class attribute.

How I can put unspecific class tag with execCommand method in IFRAME ? If somebody now any solution for it i'll be grateful.

For example:

When I selected some text from IFRAME I wish receive this
<P class=xyz>selected text</P> ON SAME PLACE WHERE SELECTED TEXT WAS.

Problem with this function is because that put selected text to end of page. How I can put text on same place ?

function InsertClass (cmd,opt) {

var strStart,strEnd,A;

//copy selected text to clipboard
idContent.document.execCommand('copy',"",opt);

strStart="<P class=xyz>";
strEnd=</P>;

// convert TextMode in HTMLMode
A=idContent.document.body.innerHTML;
idContent.document.body.innerText=A;
idContent.focus();


idContent.document.execCommand('paste',"",strStart);
idContent.document.execCommand('paste',"",opt);
idContent.document.execCommand('paste',"",strEnd);

// convert TextMode in HTMLMode
A=idContent.document.body.innerText
idContent.document.body.innerHTML=A;
idContent.focus();

}

Sorry about my little english.

Eny suggestion?