Drop Down List (Data validation )_vlookup_I need to chose from anther list

I am not certain that I have interpreted correctly. So I am guessing somewhat.

In column I of sheet2 I made a list of unique car IDs. They are the data validation list for the new drop downs in column C of sheet1.

In cell J2 of sheet2 I array-entered this formula and filled / copied down and across to K39:

Formula:

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Array enter means the formula must be committed by simultaneously pressing and holding down Ctrl and Shift while hitting Enter.

Referencing the array range in sheet2 I redefined the drop down validations in column D of sheet1 to

Formula:

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in Data Validation Manager Source text box.

Now when you select a car ID in column C the drop downs in column D are limited to those drivers assigned to that car.

Does this do what you want?

And I must ask: Though your profile says Excel 2003 your uploaded file is an *.xlsx file. If backwards compatibility is to be considered my array formula in sheet2 will need to be reworked. Excel 2003 does not recognize the IFERROR function. Do you require backwards compatibility?

The file is attached.

I have changed the lookup / data validation formula in sheet 2 to include column P and also changed the range of CarID definition to accept additional driver assignments. That range is now B2:B1000.

To demonstrated I added a fictitious driver to the end of the DriverName list in sheet 2 assigned to car 7672. That additional driver now shows up in the lookup / data validation list in sheet 2 and therefore in the drop down of D2 in sheet 1 when car 7672 is selected in cell C2.

The workbook is attached.