A system variable I can write to.

I would like to create a variable in a function I can write to.

For example in a bet trigger I will call a function. LayRise(@best_lay_price)

Inside the function I would like to save the @best_lay_price to system variable so the next time the function is called, I can see if the price has increased since the last time.

If I simply create a variable in SysVariables like @lay1, can I then inside the function write to it?


set @lay1 = @best_lay_price;

so all of it would be 


declare @rise bit;
set @rise = (@lay1 < @best_lay_price);

-- save the price for next time...
set @lay1 = @best_lay_price;


RETURN @rise;
SysVariable:

[Name] lay1
[Declaration] declare @lay1 numeric(18,2)
[Funct] select @lay1