How do i loop by offsetting range by 1 row

How to I increment the x and y data sets by one?
-------------------

    Sub main_ols()
    Dim x, y, z,
    Dim strMsg As String


    For x = 2 To 500

    x = RangeToArray(Sheet4.Range("B2:B51"))
    y = RangeToArray(Sheet4.Range("C2:C51"))

    z = regress_orthols(x, y)

    strMsg = "1.slope" & vbTab & z(1) & vbNewLine
    strMsg = strMsg & "2.intercept" & vbTab & z(2) & vbNewLine
    strMsg = strMsg & "3.sigma_slope" & vbTab & z(3) & vbNewLine
    strMsg = strMsg & "4.sigma_intercept" & vbTab & z(4) & vbNewLine

    MsgBox strMsg, vbInformation, "Least-squares Orthogonal Regression Result"

    Sheet4.Range("slope") = z(1)
    Sheet4.Range("intercept") = z(2)

    z = regress_ls(x, y)

    strMsg = "1.slope" & vbTab & z(1) & vbNewLine
    strMsg = strMsg & "2.intercept" & vbTab & z(2) & vbNewLine
    strMsg = strMsg & "3.sigma_slope" & vbTab & z(3) & vbNewLine
    strMsg = strMsg & "4.sigma_intercept" & vbTab & z(4) & vbNewLine

    MsgBox strMsg, vbInformation, "Least-squares Regression Result"
    Next
    Set x = RangeToArray("B2:B51").Offset([1], [0]).Select

    Set y = Range("y").Offset(1, 0).Select

    z = regress_orthols(x, y)
    Set z(1) = Sheet4.Range("slope").Offset(1, 0).Select
    Set z(2) = Sheet4.Range("intercept").Offset(1, 0).Select
    Sheet4.Range("slope") = z(1)
    Sheet4.Range("intercept") = z(2)