Need Script! Unknown/Unset Integer

I am currently trying to build a script, but I am not sure how to even start it.

It needs to have a string that will be set to a value (example: "interger" Cat = 50)

Then I need the script to be listening for an integer to be stated, this integer is unknown and unset by the script.

When the script hears this unset integer it needs to subtract it from the string (example: I say 7 and the script takes "interger" Cat = 50 and subtracts 7 and now "integer" Cat = 43)

This is really alot to ask for I understand but if I could get this it would take a world of stress off my sholders. Thank you so much!

something along the lines of this example?

integer Cat;

default
{
	state_entry()
	{
		Cat = 50;
		llListen(0, "", llGetOwner(), "");
	}
	
	listen(integer channel, string name, key id, string message)
	{
		Cat -= (integer)message;
		llOwnerSay("Value of Cat is " + (string)Cat);
	}
}