Dynamic Data Validation lists based on VLookup - excel

Question

I'm trying to add a custom 'discount' list to my spreadsheet.
I've got a table that contains all the data, and has costs for the standard 'used' value, then also the values at a 5% discount and a 10% discount.
Example:
+---------+-------------------+------+------------+-------------+
| Code | Role | Used | Used - 5% | Used - 10% |
+=========+===================+======+============+=============+
| Test001 | Employee | 5.67 | | |
+---------+-------------------+------+------------+-------------+
| Test002 | Junior Technician | 9.80 | 9.31 | 8.38 |
+---------+-------------------+------+------------+-------------+
| Test003 | Project Manager | 15 | | |
+---------+-------------------+------+------------+-------------+
| Test004 | Engineer | 20 | 19 | 17.10 |
+---------+-------------------+------+------------+-------------+
I've then got a Data validation list which returns all other the 'Roles' to select from. On the back of this this populates the Cost cell.
Example:
+----------+----------+----------+-------+
| Role | VLOOKUP | Discount | Cost |
+==========+==========+==========+=======+
| Employee | | | 5.67 |
+----------+----------+----------+-------+
| Engineer | 5%,10% | 10% | 15.10 |
+----------+----------+----------+-------+
What I want to do is have a list to be populated with 5%, 10% if there is that option. I'd like to achieve this without vba (I could easily achieve this with vba but trying to keep it all in the worksheet)
My VLOOKUP Column is populated using:
=CONCATENATE(IF(VLOOKUP(A2,INDIRECT("Test[[Role]:[Used - 10%]]"), 3, FALSE) <> "", "5%", ""),
IF(VLOOKUP(A2,INDIRECT("Test[[Role]:[Used - 10%]]"), 4, FALSE) <> "", ",10%", ""))
The issue comes when trying to do the data validation. It accepts the formula (tried using the above to no avail in the data validation) but populates the drop down list with just the one value of 5%,10% instead of interpreting it as a csv.
I'm currently using this to attempt to populate the Discount Drop Down
=OFFSET(INDIRECT(ADDRESS(ROW(), COLUMN())),0, -1)

Answer 1

It is possible assuming your version of Excel has access to the dynamic functions FILTER and UNIQUE. Let's go through a couple of things, and here is a google doc where this is demonstrated. I also included an online excel file*.
It isn't necessary to calculate the cost in the setup table (A:E). You can just use a character to mark availability (and in some versions it was difficult to make the FILTER work with comparisons like <>"", etc, when ="x" worked fine).
You can get an array of available discounts by using FILTER, INDEX and MATCH. See Col P. You use INDEX/MATCH to return a single row of the array containing the discounts (in this case D:E), and then use that row to filter the top row (D1:E1) which has the friendly discount names and return it as an array.
It isn't necessary to concat the discount list the way you're doing. You can use TEXTJOIN, FILTER, INDEX and MATCH. See Col I. You just wrap the calculation that generates the array of discount names (step 2) in TEXTJOIN to get a string.
The validation is accomplished by referencing the output of step 2. I don't think that the data validation dialog can handle the full formula, so I pointed it to Cols O:Q. Col O is included in the validation so that you can get an empty spot at the top of the list, but Google Docs seems to strip it out.
You can just calculate the discounted cost from the selected option. See Col K. I included the original cost in Col L so you can see it.
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