Unique drop down list
 

I have a number of projects, divided into 4 stages - start; midway;
completion; defects.
How can I create a unique list of job numbers from a growing list of projects
I use named ranges generally, but this give me a list of all records & the
project number appears several times in different positons on the list
I want my users to select a project number from a drop down list (data
validation) to lookup details against - ideally in order

Data entry view
Project Stage
1 Start
2 Start
3 Start
1 Midway
2 Midway
3 Midway
1 Completion

Any ideas