>I was thinking about combining 2 sys(3) values to create a key but I have seen negative and non unique values from sys(3).

SYS(2015) gives you unique IDs, no matter how fast you issue it.

If you prefer the kind of value generated by sys(3), you can just use:

*------------------------------------
* Function...: UniqueID
* Author.....: MARTIN
* Date.......: 18/02/1998
* Notes......: Generates a unique name. As SYS(3) can generate the same value
*            : when issues in the same millisecond, this function throws the first
*            : one and returns the second.
* Parameters.: None
* Returns....: A unique ID name
* See Also...: 
* 
local lcRetVal
lcRetVal = sys(3)			&& Takes the first value

do while lcRetVal = sys(3)		&& Waits for a different one
enddo

lcRetVal = sys(3)			&& Returns the safe one (or the next!)

return lcRetVal
*-------------------------------* Fin 

Hope this helps,