Am I using the isnumeric function correctly? - vba

Question

This program is to convert a column of data from cumulative to non-cumulative. On my sheet I have A1, B1, and C1 with the text Non-Cumulative, Cumulative, and Converted, respectively. I have numbers 1 to 10 beneath A1, then them summed cumulatively beneath B1. C1 is where I want to convert column B back to non-cumulative.
The IsNumeric is used to make the first row of data in C equal to the first row of data in B. It should detect that the title is above the number it is evaluating, thus knowing that no calculations have to be performed. For the rest of them, it'll see that the number above the one it is evaluating is a number, and thus the calculation has to be done.
My problem is that it isn't working. I think the reason is because IsNumeric() keeps coming back as false. Is there a different function I should be using? Do cell references not work in IsNumeric?
Here's the program!
Option Explicit
Dim i As Variant
Sub Conversion()
Sheets("Test Sheet").Select
For i = 1 To 10
If IsNumeric("B" & i) = False Then
Range("C" & i + 1) = Range("B" & i + 1)
Else: Range("C" & i + 1) = Range("B" & i + 1) - Range("B" & i - 1)
End If
Next
End Sub

Answer 1

The way you wrote your code is logical, just a minor syntax changes you need initially. However,
It's also best to check if the range is empty first...
Then check on if the value is numeric.
Better even, if you set the Range into a Range object and use offset
Code:
Option Explicit '-- great that you use explicit declaration :)
Sub Conversion()
Dim i As Integer '-- integer is good enough
Dim rngRange as Range
'-- try not to select anything. And for a cleaner code
Set rngRange = Sheets("Test Sheet").Range("B1")
For i = 1 To 10
If (rangeRange.Offset(i,0).value) <> "" then '-- check for non-empty
If IsNumeric(rangeRange.Offset(i,0).value) = False Then
rangeRange.Offset(i+1,1) = rangeRange.Offset(i+1,0)
Else
rangeRange.Offset(i+1,1) = rangeRange.Offset(i+1,0) - rangeRange.Offset(i-1,0)
End If
End if
Next i '-- loop
End Sub
To make your code more dynamic:
Another suggestion, you may simply Application.WorkSheetFunction.Transpose() the entire B column range that you need to validate into a variant array
Process the array and Transpose back to the Range with column B and C.
By doing so, you may omit setting for loop size manually but setting it using Lower and Upper bound of the array ;)

Answer 2

You need to check if the range of B i is numeric, not the string "B" & i
and rather than selecting the sheet, simply using a parent identifier like:
sheets("sheet1").range("B" & i)
This will help you avoid errors in your code
For i = 1 To 10
If IsNumeric(sheets("test sheet").range("B" & i).value) = False Then
Range("C" & i + 1) = Range("B" & i + 1)
Else: Range("C" & i + 1) = Range("B" & i + 1) - Range("B" & i - 1)
End If
Next