Show attachment message in a sequence format

I have a page, on which if I submit the form without adding the attachment, I get message as "Please attach file for .., .., .., "
But now I want to show that in a sequence like below:-
Please attach file for
SR.No  AttachmentName   Attached(Y/N)   1.                Passport                      Y

Here is my code below:-
if (strerrmsg != "") { Page.ClientScript.RegisterStartupScript(typeof(Page), "CloseScript", "alert('Please Attach file for " + strerrmsg.ToString() + " ');", true); // how to set sequence here ?? }