APEX

I would like to run a process when a button is pressed, but I only want the button to display after a popup lov value is selected and before it is submitted. The default value for the popup lov is null. I can see the value is null in session state and I can see the value in session state after lov selection. I can't seem to get the button to not display when session state for LOV item is null. The idea is to prevent the user from clicking the button to run the process if nothing is selected in the lov.

At the same time i want to reset the LOV item to null so the button/process is not inadvertently run again using the same value previously selected.

I like the lov better than select list with submit because I can search and display many concatenated columns while returning only the key column.

Is it possible to display a button conditionally based on an LOV selected value or null, prior to submit, and if so, how?