crystal reports how do you include null columns in your report

[Crystal]

I was wondering if anybody here has experience with using Crystal Reports

I put together a report and added a filter which goes something like:

{transfer_log.previous_department}<>"G&A"

This works and the report indeed eliminates rows with employees who's previous department is General and Administrative.

HOWEVER, it also eliminates rows in which employees had no previous departments and I need to get those in the report!

I went to the formula editor and tried all of the following:

NVL({transfer_log.previous_department},"xxx")="xxx " or {transfer_log.previous_department}<>"G&A"

{transfer_log.previous_department} IS NULL or {transfer_log.previous_department}<>"G&A"

{transfer_log.previous_department}="" or
{transfer_log.previous_department}<>"G&A"

but none of these work!

anyone know how I can achieve what I need?