Link G/L Entry with Item-number

Hi

I have a problem where I need to export an xml-file from G/L Entry and some how generate one field from Item no. if one has been used.

I'm aware that if for example a sales invoice uses multiple items which shares same dimension set-id, the G/L entry will be combined to one entry.

Is there a effortless way to link G/L entry to Value entry? Most painless way must be create a dimension out of Item no. and and make it mandatory to every item posting?

Br,

pn7