How to line up a merged field to a column heading

[j_Southern]

I am trying to produce proforma invoices.


This involves lining up merged fields such as "quantity", "Unit Price", "Net Price"
under headings. I have used picture switches to ensure the formats are right but the varying lengths of the formatted fields dictates their position rather than the column heads.
So the merge document looks like this

Quantity Unit Price Net Price
<Qty> <Unit_Price> <Net_Price>

The result can look like this
Quantity Unit Price Net Price
12 1.00 12.00

How can I get the result I want ?
John