Prevent double entries

Situation:
A Computed <a href...> defines to open document or when is does not exists to create a new document.

Problem:
When new doc is created and link has not been refreshed, the user could create a double entry.

I ran into situation where only one comment is allowed per field on a form.

Solution:
An webqueryload agent checks if the document already exists and if so, it fills a field in the new document with the reference to the existing (new) form.

The Onload event of that form checks if the reference exists and if so, it changes the contents to the existing form.

This way you can prevent a user from submitting a new form twice.

Be careful, the page header must contain expire info.

This way you prevent that a double entry is made ( Although a webquerysave agent should doublecheck the save also)

*****************
Main Form
*****************
'HTML Header
"<script type='text/javascript'>"+@NewLine+
"function openwindow(site)"+@NewLine+
"{"+@NewLine+
"window.open(site,'my_new_window',"+
"'toolbar=no,location=no,directories=no,"+
"status=no,menubar=no,scrollbars=no,resizable=no,copyhistory=no,width=460,height=340')"+@NewLine+
"}"+@NewLine+
"</script>"+@NewLine

'Computed Href
Fnm:="MyComment";
@If(!@IsNewDoc;

@If(!@IsError(@DbLookup("";"";"C1";@Text(@DocumentUniqueID)
Fnm;2));

"<a href='Javascript:{openwindow("+@Char(34)+"/" +@ReplaceSubstring(@Subset(@DbName;-1);"";"/")+"/2dd262338b8f9919c1256ac500360c84/"+@DbLookup("";"";"C1";@Text(@DocumentUniqueID)+Fnm;2)+"?OpenDocument"+@Char(34)+")}'><IMG SRC='/icons/vwicn005' Border=0></a><br>";

@If(@IsDocBeingEdited = 1;"<a href='Javascript:{openwindow("+@Char(34)+"/" +@ReplaceSubstring(@Subset(@DbName;-1);"";"/")+"/frmComment?OpenForm&ParentUNID="+@Text(@DocumentUniqueID)+ "&" +Fnm+@Char(34)+")}'><IMG SRC='/icons/vwdrafts.gif' Border=0></A>";" ") )
;"")

************************
Comment/New form ( response )
*************************

'Prevent that browser uses cached form
HTML Head Content:
"<meta http-equiv='expires' content='Tue, 04 Dec 1993 
21:29:02 GMT'>"


WebQueryOpen:
@Command([ToolsRunMacro]; "QSWebCommentOpen")


Onload:

var f = document.forms[0];


if (typeof f != "undefined")
{
 if ( f.Exists.value=="99") {
location=f.OrgLink.value+"?Opendocument";
	}
}




*******************
Agent used 
******************
%REM
	This agent checks during load if a response form 
        for the specific field already exists.
        Since Notes Ignores a print comments, a value is set 
        on the form itself then the load event acts on this 
        value. You cannot use hide section stuff, cause the 
        HTML is already there.
%ENDREM
	
	
	
	Dim currentDoc As CurrentWebDocument
	Dim db As NotesDatabase
	Dim viewValidation As NotesView
	Dim ValidationCollection As NotesDocumentCollection
	Dim WdocPath As Variant
	Dim docValidation As NotesDocument	
	Dim RespID,NRespID As String
	
	Set currentDoc = New CurrentWebDocument("")
	WdocPath  = currentdoc.doc.getitemvalue("zzDBPath")	
	Set db=currentdoc.doc.Parentdatabase
	dbserver = db.server
	If Dbserver = ""         Then 
		dbserver = "LocalHost" 
	Else
		DbServer = Mid(dbserver,Instr(dbserver,"=")+1)
		DbServer = Left(dbserver,Instr(dbserver,"/")-1)
	End If
	RespId = currentdoc.doc.query_string(0)
	RespId = Mid(RespId,Instr(RespID,"=")+1)
	NRespId = Left(RespId,Instr(RespID,"&")-1)
	NRespId = NRespID+Mid(RespId,Instr(RespID,"&")+1)
	Set viewValidation=db.GetView("C1")
	Set ValidationCollection = viewValidation.GetAllDocumentsByKey(NRespID  ,False) 
	If ValidationCollection.Count <> 0 Then
		Set docValidation=ValidationCollection.Getfirstdocument
		currentdoc.doc.Exists= "99"
		currentdoc.doc.OrgLink =  "http://" +dbserver + "/"+WdocPath(0)+"/"+Cstr(viewvalidation.UniversalID)+"/" +Cstr(docvalidation.UniversalID)
	Else
		currentdoc.doc.Exists= "00"
	End If
End Sub