Copy a child record that contains a Multi-Line Text Field.

I working on a quote form and need to ability to copy a child record on the quote.
(Quote being the parent, and Details being the child records).

I can get it working just fine with the following URL Formula:

var text URL= URLRoot() & "db/" & Dbid() & "?a=API_AddRecord"
& "&_fid_15=" & [Related Sales order]
& "&_fid_13=" & URLEncode([Related Product])
& "&_fid_7=" & URLEncode([Product Description2]) //this is a lookup field
& "&_fid_8=" & [Product Quantity]
& "&_fid_9=" & [Product Unit Price]
& "&_fid_24=" & ToNumber([Taxable Item]);

"javascript:" &
"$.get('" & 
$URL & 
"',function(){" &
"location.reload(true);" &
"});" 
& "void(0);"

(FID #7 is the ID for [Product Description] a multi-line text box).

[Product Description2] is a lookup field that pulls in a default product description from a products table.  Using form Rules, I then copy this value to a field called [Product Description] which is multi-line text box.  This allows the sales reps to edit the product description as needed, and this is what is displayed on the quote.

What I really need is this URL Formula to work:

var text URL= URLRoot() & "db/" & Dbid() & "?a=API_AddRecord"
& "&_fid_15=" & [Related Sales order]
& "&_fid_13=" & URLEncode([Related Product])
& "&_fid_7=" & URLEncode([Product Description]) // this is a multi-line text box.
& "&_fid_8=" & [Product Quantity]
& "&_fid_9=" & [Product Unit Price]
& "&_fid_24=" & ToNumber([Taxable Item]);

"javascript:" &
"$.get('" & 
$URL & 
"',function(){" &
"location.reload(true);" &
"});" 
& "void(0);"

But when I change [Product Description2] to [Product Description] - The URL Formula no longer works (no errors, just don't work).

The only reason I can think of is maybe it is because it is a Multi-Line Textbox.
Any Ideas??

Thanks

Mark