EXCEL HELP:

I want to automatically increase the session number to +1 if a customer is shown again in the list.

so if I put John in again the session number will come up as 2. It would increase the number of times a customer is repeated in the session column as shown below:

So what would be the formula for it? I have tried Countif but didn't work well.

I have manually added 2 when john is repeated, I want to automate it.

\begin{tabular}{|l|c|} \hline \multicolumn{1}{|c|}{ Client Name } & session \# \\ \hline John & 1 \\ \hline Clare & 1 \\ \hline Adnan & 1 \\ \hline Sara & 1 \\ \hline Anthony & 1 \\ \hline John & 2 \\ \hline \end{tabular}