C# ASp.net InputFormTextBox Html issue

Hi,
I used following code to create  InputFormTextBox, When i copy from excel sheet some records it will automatically creating
unnessary codes. See below

<P>
<TABLE style="WIDTH: 48pt; BORDER-COLLAPSE: collapse" cellSpacing=0 cellPadding=0 width=64 border=0>
<COLGROUP>
<COL style="WIDTH: 48pt" width=64>
<TBODY>
<TR style="HEIGHT: 17.25pt" height=23>
<TD style="BORDER-TOP: #f0f0f0; HEIGHT: 17.25pt; BORDER-RIGHT: #f0f0f0; WIDTH: 48pt; BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: transparent" height=23 width=64><FONT face=Calibri>Test<FONT class=font5><SUP>2</SUP></FONT></FONT></TD></TR></TBODY></TABLE></P>


I need only copying and paste to InputFormTextBox ,Please some one show me how to do.I already Ask user to enter
starting point £ and end of sentance £,throught that im removing HTML code,But its time consuming,so any one show me any better way or how to avoid this issue
Expected Results

Test<SUP>2</SUP>

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Seebelow my C# code How to creating InputFormTextBox

private InputFormTextBox richTextEditor

     richTextEditor = new InputFormTextBox();
            richTextEditor.RichText = true;
            richTextEditor.RichTextMode = SPRichTextMode.FullHtml;
            richTextEditor.TextMode = TextBoxMode.MultiLine;
           

            richTextEditor.Width = System.Web.UI.WebControls.Unit.Percentage(100);  
            richTextEditor.Rows = 10;
           
            richTextEditor.Enabled = true;
            richTextEditor.Visible = true;
            //Panel1.Controls.Add(richTextEditor);
            Panel_Disclaimer.Controls.Add(richTextEditor);