Finding duplicates and adding their adjacent cells

Hi, I'm very new to vba and haven't found a thread that matches exactly what I need, although I apologise if this has been discussed before.

I have thousands of rows to compare each time. I need to find duplicate entries in column A and then add their values which are in column B to put in column C. There is only one worksheet each time.

Col A can be numbers only or a mixture of numbers and letters. It starts looking like:

Col A Col B
THH1234 1
TKK254 1
124892 2
6935 1
6935 5
C09654 2

I want it to end like this below where 6935 are recognised as duplicates and their values of 1 & 5 added to be 6. It doesn't matter if the 6 is in the row for the first or second duplicate.

Col A Col B Col C
THH1234 1
TKK254 1
124892 2
6935 1
6935 5 6
C09654 2

It would be ideal if I didn't have to sort column A so that duplicates are next to each other before running the macro but that's not important. Thanks any help is appreciated.