Difficult Lookup formula

Hello,

I have a difficult question that may not have an answer. At least, I haven't found a formula that works.

A B C
1 RC002 RC003 RC004 1 3

2 RC005 RC006 2 4

3
A B C
4 RC002 RC004 2 4
5 RC003 2 4
6 RC005 RC006 3 5

As you see, RC003 is no longer grouped with RC002 RC004 in the bottom part in column A
Column B indicates how many times Item in column A (RC002 RC003 RC004) has appeared. For this example, In the top part it arrears once. In the second part, it now has appeared twice.
Column C calculates consecutively it has appeared. For example in the top part, RCOO2 RC003 RC004 is at 3, but in the bottom part, RC003 no longer is in that group, but they were in the top part, so in column C, RC003 should be 3. If I use the vlookup(RC003 (A7), A1:C3,3,True, I would get 4 instead of 3.

This is pretty difficult to explain, and I'm sure I didn't explain myself well.