Possible array IF formula

I have a list of references in col a a1:a100, howver there are some duplicate references. In col b1:b100 an action of either "check" or "exclude" sits next to the reference.

I need a way of determining where there is a count of duplicate references in col A, that only one type of action sits next to the appropriate refernce in col B.

I.e. if the reference A0003 appears 3 times the n the corresponding action siting alongside col b is either check x3 or excludex3. Where there is a combination I.e. Check Check Exclude. I need a away of creating a flag in col C

Unfortunaetly I am unable to upload a sample, but any help would be appreciated.

Thanks

Ted

Cheers Tony that works a treat