Here is a solution that uses no worksheet functions
Option Explicit
Sub SelectLastMonthsPrices()
'Date / price columns must be sorted ascending before running sub
Dim FirstCel As Range
Dim LastCel As Range
Dim FirstDay As Date
Dim LastDay As Date
Dim Cel As Range
Dim WholePreviousMonthPrices As Range
'Range("A:B").Sort Header:=xlYes
FirstDay = DateAdd("m", -1, Format(Date, "mm/1/yyyy"))
LastDay = DateAdd("d", -1, Format(Date, "mm/1/yyyy"))
Set FirstCel = ActiveSheet.Cells(2, 1)
Do While FirstCel < FirstDay
Set FirstCel = FirstCel.Offset(1)
Loop
Set LastCel = FirstCel.End(xlDown)
Do While LastCel > LastDay
Set LastCel = LastCel.Offset(-1)
Loop
Set WholePreviousMonthPrices = Range(FirstCel, LastCel).Offset(0, 1)
WholePreviousMonthPrices.Select
End Sub