how to solve index was outside the bounds of the array in vb, see below coding

Private Sub btnRead_Click(sender As Object, e As EventArgs) Handles btnRead.Click
    Dim F As Integer
    Dim P As Integer

    For F = 1 To NumFarmers
        MarsFarmers(F).Name = InputBox("Please enter farmer name" & CStr(F))
        MarsFarmers(F).Workers = CInt(InputBox("Please enter number of workers" & CStr(F)))
        For P = 1 To NumPeriods
            MarsFarmers(F).Profit(P) = CInt(InputBox("Please enter profit of farmer" & CStr(F)))
        Next P
    Next F
End Sub