hello all. i appreciate it if someone can help me with the question below

i have a drop down list (P) with values A,B,C
another drop down list (s) with values 1,2,3
another equation that reads from drop down list (S)

can i make the drop down list (S) reads the value and changes based on the (P) drop down list selection, and the the equation reads the value of what will show up in the drop down list (S)

thanks in advance