previousValue dataset memory tag event script

Dear All
I have simple question
I have memory tag as dataset, i would like to create tagEventScript where i read the previousValue[0,1].value

something like

params = {"factoryNumber":str(int_factoryNumberValue[0].value), "stations":"1-2","size":previousValue.getValueAt(0,1)}

but iam trying and iam unable to achive this in script.

I am unable to read single dataset values from previous or current value in dataset memory tags

normaly i do something like this

int_rowCountValue = system.db.runNamedQuery(XXXX,XXX,params)|
if int_rowCountValue.getValueAt(0,0) >= 1:

but iam unable to achive this for previousValue

Thank you for your help

int_previousValue = previousValue.value