Cómo que no es posible? mirá que si!!!
<%
Response.Write "<script language=" & CHR(034) & "JavaScript" & CHR(034) & ">"
Response.Write "if (document.all)"
Response.Write "document.body.onmousedown=new Function(" & CHR(034) & "if (event.button==2||event.button==3)alert('No funciona!')" & CHR(034) & ")"
Response.Write "</script>"
%>
:P ;)