Print Line No in single line instead of multiple lines

Hi,

in for each group line No Print in Multiple Lines like this

1

2

3

4

but i have to print line No in Single Line like this

1, 2, 3, 4

My XMLP Code at PO line level is:

<?for-each-group:G_LINE_NO;./TAX_RATE?>

<?TAX_TYPE?> @ <?TAX_RATE?>%

<?for-each-group:current-group();./LINE_NO?>

<?LINE_NO?>

<?end for-each?>

<?sum(current-group()/TAX_AMOUNT)?>

<?end for-each-group?>

Please Advise Me

Regards,

pavan k