Una primera idea. El resto es jugar...
Código HTML:
<html>
<head>
<script>
document.write("<table border='1' cellpadding='1' cellspacing='0'>\n");
document.write("<tr>\n");
for (s=0;s<=24;s++){
document.write("<td align='center' width='4%'>"+s+"</td>\n");
}
document.write("</tr>\n");
for (r=1;r<=7;r++){
document.write("<tr>\n");
for (s=0;s<=24;s++){
document.write("<td style='cursor: pointer;' onClick='javascript: alert("+r+","+s+");'> </td>\n");
}
document.write("</tr>\n");
}
document.write("</table>\n");
</script>
</head>
<body>
</body>
</html>