Range of inputs and graphing of result

[Itakeyokes]

Thank you for your reply and sorry for such a delay in getting back to you.

This code works as desired for that purpose.

 Sub test()    
Dim V As Double
lastrow = Cells(Rows.Count, "A").End(xlUp).Row
inarr = Range(Cells(1, 1), Cells(lastrow, 3))
For i = 2 To lastrow
    V = inarr(i, 3)
    Cells(i, 7) = X(V)
Next i
Worksheets(1).Range("G1").Value = "dP / L"
End Sub
 
 
Function X(V As Double) As Double
 X = V * Worksheets(1).Range("E2") / Worksheets(1).Range("D2")
End Function       'Here the constant values are brought from the worksheet, whilst the variable input is still accounted for.

For a similar situation, but for one where there is only one variable, is the above code as efficient/correct as it could be?

Here column C has the rising values for V, but column A, B, D, E etc contain constants.

This code works with this set up.

However, I have applied it to another scenario on another worksheet and it does not run.

Sub test2()
Dim Nr As Double
lastrow = Cells(Rows.Count, "A").End(xlUp).Row
inarr = Range(Cells(1, 1), Cells(lastrow, 10))
For i = 4 To lastrow
    Nr = inarr(i, 10)
    Cells(i, 16) = DIP(Nr)
Next i
End Sub
 
Function DIP(Nr As Double) As Double
DIP = 1 + ((1.996 * 5) / Nr)
End Function

Here, the varying input is in column J starting at row 4. The constants have been inputted manually.

Thanks,
ITY