Unique entries down a column

Hello,

I maintain a list of bugs in a spreadsheet. Each row consists of a bug. The data is entered as a bug report is received.

Each Column has different kind of data for a bug e.g. Date of reporting the bug in one column, reported by in another, description in a third, the module in which the bug was reported and so on.

As we all know too well ;-( , more than one bug can occur in the same module.

Using formulas only, is it possible to get a list, in a different column, of all modules in which bugs have been reported and more importantly, (and this is the crunchy part for me), get a UNIQUE list, in consecutive rows, with no module repeated in that list?

To explain

The "Module" column may contain the following data:

Add User
Add User
Add User
Delete User
Modify User
Modify User
Delete User
Print User

The new / unique list should consist only of

Add User
Delete User
Modify User
Print User

I have a formula to get a unique list .. but I am not able to come up with a list in Consecutive rows.

So my list for the example above would read something like:

Add User
<BLANK CELL>
<BLANK CELL>
Delete User
Modify User
<BLANK CELL>
<BLANK CELL>
Print User

Hope to hear soon.

Thanks in advance.