A smart way to use "$" in data frame

Hello all,

I have a data frame dataa:

newdate newstate newid newbalance newaccounts
1 31DEC2001        AR         1                 1170           61
2 31DEC2001        VA         2                  4565           54
3 31DEC2001        WA         3                 2726           35
4 31DEC2001        AR         3                 2700           35

The following gives me the balance of state AR:

dataa$newbalance[data$newstate == 'AR']
1170
2700

Now, I have another different data frame datab, it is very similar to data, except that the name of the columns are different, and the order of the columns are different:

oldstate olddate oldbalance oldid oldaccounts
1 AR       31DEC2012        1234         7              40
2 WA     31DEC2012        2222         3              30
3 VA       31DEC2012        2345         5              23
3 AR       31DEC2012        5673         5              23

datab$oldbalance[datab$oldstate== 'AR' ]
1234
5673

Could I have a way to quote

data$balance[data$state == 'AR']

in general, where balance=oldbalance, state=oldstate when data=dataa, and balance = newbalance, state = newstate when data=datab ?