Setting a variable range

[carstenp]

I am trying to interpolate between two values that I need to look up. The problem is that the range of values that I need to interpolate for will change. How do I set a range that will adjust to the parameters I need it to? Also, I have left out the interpolation part so any help on this would be greatly appreciated too. This is what I have so far

max = Application.max(rng2)
For j = 1 To max
'k is the number of rows for that specific entry enabling us to set the variable range to that number of rows
    k = Application.CountIf(rng2, j)
        If c2 > 0 Then
        c1 = c2 + 1
        Else: c1 = 2
        End If
        c2 = c1 + (k - 1)
'^^^above checks out
        Set rngcurrent = Range(Cells(c1, 1), Cells(c2, 20))
 
'Interpolate for N-S and E-W at the same zD as input for others
         ' b3 = zD
         ' b1 = Application.Large(rngcurrent, Application.CountIf(rngcurrent, ">" & b3) + 1)
         ' b2 = Application.Small(rngcurrent, Application.CountIf(rngcurrent, "<" & b3) + 1)
         ' n_s1 = Application.VLookup(b1, rngcurrent, 14, True)
         ' n_s2 = Application.VLookup(b2, rngcurrent, 14, True)
         '    If b3 - b1 = 0 Then
         '    n_s3 = n_s1
         '    Else
         '    n_s3 = n_s1 + (b3 - b1) * ((n_s2 - n_s1) / (b2 - b1))
         '    End If
         ' e_w1 = Application.VLookup(b1, rngcurrent, 15, True)
         ' e_w2 = Application.VLookup(b2, rngcurrent, 15, True)
         ' e_w3 = e_w1 + (b3 - b1) * ((e_w2 - e_w1) / (b2 - b1))