jnix try this:
under format there are 4 possible choices positive, negative, zero, and null enter each choice as you would like. For currency try this:
$#,###.##;($#,###.##);$0.00;$0.00
This would be your format for all 4 types: positive, negative, zero, and null. To replace the zero with blanks try this:
$#,###.##;($#,###.##);"";""
Hope this helps