File open from network not download

[tan123]

Hi,
In my asp.net application (an inhouse software) I want users to be able to use files from Network (filepath stored in database). I use the following code to download the files:

string strAttachmentID = ((Label)GridViewNotes.Rows[GridViewNotes.SelectedIndex].FindControl("lblAttachmentID")).Text;
int AttachmentID = Convert.ToInt32(strAttachmentID);
Attachment attachment = Attachment.GetAttachment_ByAttachmentID(AttachmentID);


string str = @"\\" + attachment.FilePath;
if (File.Exists(str))
{
Response.AppendHeader("content-disposition",
"attachment; filename=" + attachment.FileName);
Response.ContentType = attachment.ContentType;
Response.TransmitFile(str);
}
else
{
//message box
Response.Write(@"<script language='javascript'>window.alert('Error Downloading: \n The following file does not exist: " + attachment.FileName + " .');</script>");
}


Response.End();

Is there anyway to open the file without downloading it in a web based application, i.e. open the file directly from the network so when the users edit it and save it, the actual file is changed.
Thanks,
Tan