Using OR with IF to test for several possibilities

Hi, this is related to a thread that daffodil11 kindly solved earlier: http://www.excelforum.com/excel-form...ml#post3849778

How can I structure an IF statement with OR so that it returns "true" for more than one condition: Data!$A$2:$A$20=B2 OR Data!$A$2:$A$20=A2 ?

The function I have now

{=IFERROR(STDEV(IF(OR(Data!$A$2:$A$20=B2,Data!$A$2:$A$20=A2),Data!$B$2:$B$20)),"Not Enough Data")}

seems to calculate on ALL the states shown in the data tab.

Hopefully the sample workbook attached helps illustrate.

Thank you