PLD: Position no. of items instead of LineNum()

Hello,

I have a problem concerning LineNum() in PLD.. I only want to show the position no. of items and alternative items in a quotation. If I use LineNum, it regards text lines as positions, too.

For example, first row is item A10004, second contains additional text and third row contains an item A10003.. Then the item A10004 is no. 1, text line has no number, and third line continues with 2...

How can I count the rows only for the relevant (alternative) items?

Thanks in advance,

Sebastian