[Hỏi] Hàm lập bằng VBA này có tác dụng gì

Public Function Tlookup(Ta As Range, Noc As Double, Nor As Double) As Double
Dim N, m, i, i1, j, j1 As Integer
Dim minr, maxr, minc, maxc, r1, r2 As Single
Dim Ra As Range
Dim ca As Range
N = Ta.Rows.Count - 1
m = Ta.Columns.Count - 1
Set Ra = Ta.Offset(, 1).Resize(1, m)
Set ca = Ta.Offset(1, 0).Resize(N, 1)
Set Ta = Ta.Offset(1, 1).Resize(N, m)
minr = Application.WorksheetFunction.Min(Ra)
maxr = Application.WorksheetFunction.Max(Ra)
Select Case Nor
Case Is <= minr
    If Ra.Cells(1, 1).Value = minr Then
        i = 1
        i1 = 1
    End If
    If Ra.Cells(1, m).Value = minr Then
        i = m
        i1 = m
    End If
Case Is >= maxr
    If Ra.Cells(1, 1).Value = maxr Then
        i = 1
        i1 = 1
    End If
    If Ra.Cells(1, m).Value = maxr Then
        i = m
        i1 = m
    End If
Case minr To maxr
    i = 0
    If Ra.Cells(1, 1).Value < Ra.Cells(1, m).Value Then
        While Nor > minr
            minr = Ra.Cells(1, i + 1).Value
            i1 = i
            i = i + 1
        Wend
    Else
        While Nor < maxr
            maxr = Ra.Cells(1, i + 1).Value
            i1 = i
            i = i + 1
        Wend
    End If
End Select
minc = Application.WorksheetFunction.Min(ca)
maxc = Application.WorksheetFunction.Max(ca)
Select Case Noc
Case Is <= minc
    If ca.Cells(1, 1).Value = minc Then
        j = 1
        j1 = 1
    End If
    If ca.Cells(N, 1).Value = minc Then
        j = N
        j1 = N
    End If
Case Is >= maxc
    If ca.Cells(1, 1).Value = maxc Then
        j = 1
        j1 = 1
    End If
    If ca.Cells(N, 1).Value = maxc Then
        j = N
        j1 = N
    End If
Case minc To maxc
    j = 0
    If ca.Cells(1, 1).Value < ca.Cells(N, 1).Value Then
        While Noc > minc
            minc = ca.Cells(j + 1, 1).Value
            j1 = j
            j = j + 1
        Wend
    Else
        While Noc < maxc
            maxc = ca.Cells(j + 1, 1).Value
            j1 = j
            j = j + 1
        Wend
    End If
End Select
r1 = NS(Ra.Cells(1, i1).Value, Ta.Cells(j1, i1).Value, Ra.Cells(1, i).Value, Ta.Cells(j1, i).Value, Nor)
r2 = NS(Ra.Cells(1, i1).Value, Ta.Cells(j, i1).Value, Ra.Cells(1, i).Value, Ta.Cells(j, i).Value, Nor)

Tlookup = NS(ca.Cells(j1, 1).Value, r1, ca.Cells(j, 1).Value, r2, Noc)
End Function