I keep getting "Application-defined or object-defined error." Any ideas,
please help.

With Range("B3").Validation
.Add Type:=xlValidateList, _
AlertStyle:=xlValidAlertStop, _
Operator:=xlBetween,
Formula1:="=OFFSET(MarketStart,MATCH(B20,Markets,0 )-1,1,COUNTIF(Markets,B20),1)"
End With