How can I change duplicate values in a column based on the value in an another column?

[JKING]

I work for a clothing retailer. We generate a unique SKU code for each style on the basis of its attributes.

I have been able to use VLOOKUP's to generate an attribute code based on the values selected in a series of drop down lists, but now need to sequentially number any styles with identical attribute codes to create a unique SKU code for each style

For example, I may have several dresses which have identical attributes, but each one must have a unique SKU code because they are different styles.

This is made more complicated because we have several sizes of each style which must have the same SKU, so only need the sequential number to change at each change in the supplier code. Styles with identical attribute codes will not always appear together in the sheet.

Please see attached for a very basic example of the raw data and the unique SKU numbers which I have generated manually. The final result must be formatted as the SKU column in my example for our systems, but it would be fine to add another column which contains the sequential number and then use an & formula to create the final code.

Have been racking my brain to try and work out a scalable formula/function/macro which would automate this, hope someone can help!