Creating Unique ID number

Hi All,

I'm so close to having a formula work for me but fallen just short at the end:

I have A Unique ID column which i want to auto populate based on the columns [first 2 letters of category]-[3 numbers in event]-[auto list number starting from 001 and going up]

With the Code I have now i can get
DM-001
DM-001
DM-001

Which is correct however I want to add the -001 -002 and so on so it reads
DM-001-001
DM-001-002
DM-001-003

The formula im using is:

=UPPER(LEFT(D5,2)&IFERROR(MID(D5,FIND(" ",D5)+1,1), "")&"-"&LEFT(B5,3))

Any help would be great



Unique ID help.PNG