Problems with hyperlinks

I am having an issue where I have two different Acrobat forms (created in Acrobat Pro 7), I am using this.URL within app.mailMsg (see code below). The problem I am having is that 2 forms I am using produce different hyperlink types when using identical code, the first gives the full UNC path and the second giving a drive letter plus the file path (see below), the issue I have is that the form is being mailed accross sites and not all users drives are mapped to the same letter so some users are unable to open the file, does any one know how I can get hyperling type 1 consistently??

Thanks in advance for any help.
Andrew

Hyperlink type 1 (preferred)
file://///Bkmfilesvr1/Public/ECN/3261%20Walter%20Mauser%20GmbH%203pt%20Auto.pdf
Hyperlink type 2
file:///L|/Public/Acrobat%20Forms/Purchase%20Reqs/Purchase%20Req2010.pdf

app.mailMsg(false, "myuser [at] mycompany [dot] com", "", "", "ECN Number "+ECNno.value+" completed", "ECN "+ECNno.value+"(see below for details) has signed off by all relevant parties.\n\nCustomer,Project\n"+customer.value+"\n\nChange detail\n"+detail.value+"\n\nRegards\n.\nPlease click the following hyperlink to open the document:\n"+ this.URL+ "");

file://///Bkmfilesvr1/Public/ECN/3261%20Walter%20Mauser%20GmbH%203pt%20Auto.pdf

file:///L|/Public/Acrobat%20Forms/Purchase%20Reqs/Purchase%20Req2010.pdf