negative value for a db

I am trying to monitor a radio that returns a db reading in a negative 
number can someone help me in how to tell cricket collector to multiply 
the number by -1 before  passing it to rrd so that it can be shown on 
the graph?


here is a copy of my default config.

Target  --default--
   inst        =   %suid%
   snmp-community    =   XXXXXX
   snmp-host   =   %ap%
   target-type =   Subscriber-Unit

# OID's we'll be using in this tree
OID     ifInOctets     1.3.6.1.4.1.5454.1.20.3.6.1.22
OID     ifOutOctets    1.3.6.1.4.1.5454.1.20.3.6.1.23
OID     RSSIfrAP        1.3.6.1.4.1.5454.1.20.3.6.1.16

datasource  ifInOctets     ds-source   =   snmp://%snmp%/ifInOctets.%inst%
datasource  ifOutOctets    ds-source   =   snmp://%snmp%/ifOutOctets.%inst%
datasource  RSSIfrAP
       ds-source   =  snmp://%snmp%/RSSIfrAP.%inst%
       rrd-ds-type =   ABSOLUTE
       rrd-min         =   undef
       rrd-max         =   undef

targetType  Subscriber-Unit
   ds  =   "ifInOctets, ifOutOctets, RSSIfrAP"
   view    =   "Octets: ifInOctets ifOutOctets,
                RSSI:  RSSIfrAP"

# graph params for ifInOctets and ifOutOctets come from above



and an example of a target

target su.XXX
       suid    =    8
       short-desc    =    "XXXX"
       ap      =       "XXXXX"

the X's are just there to cover up what my company may concider private 
information


John Hutchinson

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