[xsl] Output multiple occurence into one and concatenate values

["Shaikh, Parvez" <Parvez.Shaikh@xxxxxxxxxxxxxxxxxxxxx>]

I have an XML that has 2 or more occurences of data. I want to comma
delimit the attribute values and output it only once. How do you do that
SOURCE XML
<?xml version="1.0" encoding="utf-8"?>

.
.
<purchasing
purchasing_purchasing_status=" " purchasing_acknowledged=""
>

<add_CER_PO
id="0" cer_number="" cer_created="" po_number=""
po_created="" Vendor="" />
<cost_allocation_product id="0" project="1725 - Project1" percent="12"
/>
<cost_allocation_product id="1" project="1774 - Project2" percent="1" />
<cost_allocation_product id="2" project="1755 - Project3" percent="87"
/>
</purchasing>

.
.
EXPECTED RESULT
 
I want to output this as
<purchasing>
<dbfield name="purchasing_purchasing_status" value = "" />
<dbfield name="purchasing_acknowledged" value = "" />
</purchasing>
<cost_allocation_product>
<dbfield name ="cost_allocation_product_project"
value= "1725 -
Project1,1774 - Project2,1755 - Project3" />
<dbfield
name="cost_allocation_product_percent" value="12,1,87" />
</cost_allocation_product>
 
 

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