Bootstrap

SamFares 

Try this:

Sub Resample()
    Dim NumSamples As Long
    Dim LastRow As Long
    NumSamples = Val(InputBox("How many samples do you need (31 - 500)?"))
    If NumSamples < 31 Or NumSamples > 500 Then
        MsgBox "Invalid input. Must be between 31 and 500!", vbExclamation
        Exit Sub
    End If
    Application.ScreenUpdating = False
    LastRow = Range("A" & Rows.Count).End(xlUp).Row
    Range("AG26:SH" & LastRow).ClearContents
    With Range(Cells(26, 33), Cells(LastRow, NumSamples + 2))
        .FormulaR1C1 = "=INDEX(RC3:RC32,RANDBETWEEN(1,30))"
        .Value = .Value
    End With
    Application.ScreenUpdating = True
End Sub