|In your OP you said: "Each box in my first row contains a drop down box with 4 options"|
Now you say: "in the first column, each cell contains a dropdown box"
I'm sure you can now see why I was confused.
In order to force a cell with a Drop Down box to show a specific value based on the entry in another cell, you have to use a Macro. Without the Drop Down, you could use the IF function, but you can't use a Drop Down and a formula in the same cell.
Of course, this means that all users of the spreadsheet have to have Macros enabled on their system. You cannot "force" another user's Excel application to run a macro. It has to be enabled by the user through Excel's macro security settings on their own machine.
One other item: You used the words "first column" and "second column" but you didn't specifically say which columns those were. For the code below, I assumed you meant Columns A and B. If that is not correct, change the numbers in the lines after the comments with the arrows to represent the column where the date will be entered and in the line where Complete should be shown. You must use the number of the Column, not the letter. A = 1, B= 2, AA = 27, etc.
If you change the Column numbers to match your columns, you should also change the Column letters in the green comments to avoid confusion.
Right-click the sheet tab for the sheet with the DropDowns and chose View Code. Paste this code into the pane that opens. Go back to your sheet and enter a Date in the appropriate column. I am assuming that your Conditional Formatting is already set to turn the cell Red when Complete is entered.
Private Sub Worksheet_Change(ByVal Target As Range)
'Ensure only one cell has been changed
If Target.Cells.Count = 1 Then
'Determine if change was in Column B (2)
'--> Set number in the next line to Column with Date <--
If Target.Column = 2 Then
'If a Date was entered, Set Column A (1) to read Complete
If IsDate(Target) Then
'--> Set number in the next line to Column with Drop Down <--
Cells(Target.Row, 1) = "Complete"
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