VBA : distinct values in a column and their associated distinct values - excel

Question

I'm trying to do something similar in vba which I have an idea of only in python for loops. Can someone teach me how to do this in vba, either in function or module macro please :
For each distinct values in column A4:A30, there should be no more than 9 distinct values in column C4:C30. If true, return 'OK' in cell A1. if false, return 'Error' in cell A1'
e.g As in the picture, Sam should not have more than 9 distinct fruits. Same goes to Mary
Update :
I have tried the filterxml method and unfortunately didn't seem work for me : [1] https://i.stack.imgur.com/cbmTs.png

Answer 1

Solution for excel with filter/unique formulas
Easiest way to achieve it in Excel365 is: add extra column which counts unique values (Fruits) for each Key (Names) and find maximum value in this column
Start with formula that find each non-blank which fits the key.
=FILTER($C$4:$C$30,($A$4:$A$30=A4)*($C$4:$C$30<>""))
Then delete duplicates:
=UNIQUE(FILTER($C$4:$C$30,($A$4:$A$30=A4)*($C$4:$C$30<>"")))
Then check how many cells we have in filtered data without blanks and duplicates:
=COUNTA(UNIQUE(FILTER($C$4:$C$30,($A$4:$A$30=A4)*($C$4:$C$30<>""))))
Then expand our new-column (column B in my case) formula to each row in our Keys.
And finally add formula to A1 which checks maximum counter:
=IF(MAX($B$4:$B$30)<10,"OK","Error - to many velues")
*There is a little typo, it should be "Error - to many values" =)
Below how the worksheet looks in my testfile
Solution for older versions of excel
I've checked if i am able to make it works without these formulas and it is possible:
We need to start with counting if there is for key-value above current row
=COUNTIFS($A$4:A4,A4,$C$4:C4,C4)
In case we have duplicates above, they should be already counted so we skip them:
=IF(COUNTIFS($A$4:A4,A4,$C$4:C4,C4)>1,"",1)
Now we have colum with "1" or blanks. In that case we need to count each non-empty cell above which correct key (name) and add 1 so instead "" and "1" we will have "" or 1, 2, 3, 4, ...
=IF(COUNTIFS($A$4:A4,A4,$C$4:C4,C4)>1,"",COUNTIFS($A$3:A3,A4,$F$3:F3,">0")+1)
Edit
I have added one extra IF to skip keys if value is blank:
=IF(C4="","",IF(COUNTIFS($A$4:A4,A4,$C$4:C4,C4)>1,"",COUNTIFS($A$3:A3,A4,$B$3:B3,">0")+1))
Cells Formula in A1 is the same
=IF(MAX($B$4:$B$30)<10,"OK","Error - to many values")
Quick Note:
Some formulas have range which starts on 3rd row instead of 4th; Its intended because we are counting cells above and at first row of data we need to have choose something above. This code assumes that you don't have numbers (on column B) or names (on column A) in row 3;
Below I am attaching screen with example; This screen have additional columns (D-F) which isn't required, its only do display how final formula was created.