Tweaking Prime[n] to return 1 when n==0

Question

I manually evaluate this cell to set Prime[0]

Unprotect[Prime]
Prime[0] = 1
Protect[Prime]   

I manually evaluate this cell to reset Prime[0]

Unprotect[Prime]
Prime[0] =.
Protect[Prime]  

In case I forget to do it, is there a way to automatically evaluate the second cell when I close the nb?

Motivation

I'm working with bags of primes and want to use $p_0$ as the bag for all prime greater than the square-root of some $n$.

Displayed as: $\left\{p_0^1,p_1^5,p_2^2,p_3^1,p_4^1\right\}$

With counts as: $\left\{1,5,2,1,1\right\}$

Answer 1

Per J.M., I did this and it works. I put it in the same cell as the setup.

SetOptions[SelectedNotebook[],NotebookEventActions ->
Quiet[{Unprotect[Prime]; Prime[0] =.; Protect[Prime];}]}];
{Unprotect[Prime]; Prime[0] = 1; Protect[Prime]};    

Edited to add the Quiet to the actions.