Mem used and Swap used using ucd/net mib

[shk14]

Hi all,


i want to get mem used and swap used values to make memory graph.
I use snmp to get the values witch ucd mib.

In ucd i got:

• memTotalSwap : .1.3.6.1.4.1.2021.4.3.0
  memAvailSwap : .1.3.6.1.4.1.2021.4.4.0
  memTotalReal : .1.3.6.1.4.1.2021.4.5.0
  memAvailReal : .1.3.6.1.4.1.2021.4.6.0

So i can get used values using formula : Total - Avail.
How can i make that with cacti if i get oids.

Thanx

PS: if you know another mib where i can directly get used memory and swap values.