VBA infinite nested for loop - excel

Question

I'm trying to write nested for loops to loop through the rows of a column to do some calculation then go to the next column to do it again. The logic makes sense to me, but the output to the sheet flashes back and forth between the correct answers and overwriting everything with the same number, and it just keeps doing that. Please let me know if I need to clarify on anything, thanks in advance.
Sub findAvg2()
Dim maxVal As Double
Dim preHr As Double
Dim nextHr As Double
Dim cVal As Double
Dim pVal As Double
Dim nVal As Double
Dim avg As Double
Dim maxAvg As Double
Dim i As Integer 'row
Dim j As Integer 'col
Dim lRow As Integer
Dim lCol As Integer
lRow = Cells(Rows.count, 1).End(xlUp).row 'Find the number of rows in column A(1)
lCol = Cells(1, Columns.count).End(xlToLeft).Column
For i = 19 To lRow
For j = 2 To lCol
maxVal = Cells(2, j).Value
preHr = Cells(8, j).Value
nextHr = Cells(9, j).Value
avg = (maxVal + preHr + nextHr) / 3
If Cells(i, j).Value > 0 Then
pVal = Cells(i - 1, j).Value
cVal = Cells(i, j).Value
nVal = Cells(i + 1, j).Value
maxAvg = (pVal + cVal + nVal) / 3
If avg > maxAvg Then
maxAvg = avg
End If
End If
Cells(12, j).Value = maxAvg
'Debug.Print maxAvg
Next j
Next i
End Sub

Answer 1

I reviewed your code and find nothing wrong with it. The modifications I did make appear to me to be of cosmetic nature. Here is the result.
Sub findAvg2()
' 005
Dim maxVal As Double
Dim preHr As Double
Dim nextHr As Double
Dim cVal As Double
Dim pVal As Double
Dim nVal As Double
Dim Avg As Double
Dim maxAvg As Double
Dim Cl As Long ' last used column
Dim Rl As Long ' last used row
Dim C As Long ' column
Dim R As Long ' row
' Find the number of used columns and roaws in the sheet
Cl = Cells(1, Columns.Count).End(xlToLeft).Column
Rl = Cells(Rows.Count, 1).End(xlUp).Row
For R = 19 To Rl
For C = 2 To Cl
maxVal = Cells(2, C).Value
preHr = Cells(8, C).Value
nextHr = Cells(9, C).Value
maxAvg = (maxVal + preHr + nextHr) / 3
cVal = Cells(R, C).Value
If cVal > 0 Then
pVal = Cells(R - 1, C).Value
nVal = Cells(R + 1, C).Value
Avg = (pVal + cVal + nVal) / 3
If Avg > maxAvg Then maxAvg = Avg
End If
Cells(12, C).Value = maxAvg
'Debug.Print maxAvg
Next C
Next R
End Sub
There is a possible weakness in this line of your code. For R = 19 To Rl. Since you are including the previous row in your calculation of averages row 18 must contain data. If it doesn't, and you can't exclude the first data row from evaluation, special provision must be made for the calculation of the initial maxAvg.
All action takes place on the ActiveSheet. This is an arrangement I instinctively dislike. Unless you are calling the sub from a button on that sheet - and even then, in case a smart alec wants to use F5 instead - I would name the sheet in the code. Use a CodeName both for greater security and to allow users the freedom to rename the sheet. This code will run on whatever sheet that happens to be active. It doesn't even have to be in the same workbook.