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.

If you are retrieving text with the VLOOKUPS() you could simply format the cells containing those formulas with this custom format: ;;"DATA"

As for the ISNA() you could use IFERROR() if you are using Excel 2007 as your profile shows.

=IFERROR(your current formula,alternative)

http://www.excelfunctions.net/Excel-Iferror.html

I tried using ISERROR and its telling me to many arguments:

=IF(ISERROR(B6="P",VLOOKUP(C6,range,2,0),VLOOKUP(C6,range,3,0)),"NEW",(VLOOKUP(C6,range,2,0),VLOOKUP(C6,range,3,0)))

Are you attempting IF(ISERROR()) because you are not using Excel 2007???
Or did you misread what I posted earlier???

If the latter - I suggested IFERROR(), not ISERROR, so try:

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

replace the "XXX" with whatever result you want in place of #N/A.