Dependent dropdown reference which allows adding values?

[a_can]

Hi there!

I don’t if it is possible but if it is then, I need a hand to create a dependent dropdown expression ordered by a/z and which allows to users to add new values even if there is the same value.

Here is the location table which located the references that I want to use in my dropdrowns.

+----------------+-----------+
| PROJECTS | BLOCS |
+----------------+-----------+
| DELTA         | A1         |
+----------------+-----------+
| DELTA         | A2         |
+----------------+-----------+
| DELTA         | A3         |
+----------------+-----------+
| BETA          | A1          |
+----------------+-----------+
| BETA          | A2          |
+----------------+-----------+
| ALFA          | B1          |
+----------------+-----------+
| ALFA          | D10        |
+----------------+-----------+

Thank you in advance