Nested If's/VLOOKUP/ISNA

The attached sample replicates an if statement that I am using which is:

=IF(OR(B4="",C4=""),"",IF(B4="P",VLOOKUP(C4,range,2,0),IF(B4="T",VLOOKUP(C4,range,3,0),"NEW?")))

Im having two issues:

1. On the table array that I reference I inserted what would be a new line of data but I intentionally left the next two columns blank. I do this because sometimes I take notes on the sheet and forget to go back and fill in the necessary columns.

Since both both B4 & C4 are true the lookup returns "O" because the fields are blank in the table.

How do I code this so that if everything is true but the data in table array is blank, the result will be "DATA?"

2. If i enter a value that is not in the table, like Z, i get #NA. I cant figure out where to put the ISNA to fix this.