invoice customisation

I am customizing a sales invoice but in doing so I am facing a few problems. It will be a great benefit if you can please help me to solve my problems.

1. I want the PartNo of the Stock Item to display in the extreme left of the invoice body part. I am setting the field as $PartNo.

2. I want the unit symbol to display in the nos column of the invoice - as it displays in the default format. I am setting the field as $UnitSymbol.

3. To display the company's VAT Number and ISST Number I am using @@CMPVATTINNumber and @@CMPISSTNumber still it is not displaying.4. I want to dispaly the Sales Order Number but failed to do so by using $other reference.

Barnali Mukherji