VBA search for corresponding line and compare values - vba

Question

I am new to VBA programming, and I am looking for a way to search a range of about 2,000 to 3,000 rows to compare quantities where ID numbers match, and generate a message box displaying the ID number if there are any matching ID numbers where quantities do not match. There are 2 matching ID numbers in the data.
I have found and adapted this code
`Dim rng1 As Range, rng2 As Range, rngName As Range, i As Integer, j As Integer
For i = 1 To Sheets("Sheet1 (2)").Range("q" & Rows.Count).End(xlUp).Row
Set rng1 = Sheets("Sheet1 (2)").Range("q" & i)
For j = 1 To Sheets("Sheet1 (2)").Range("q" & Rows.Count).End(xlUp).Row
Set rng2 = Sheets("Sheet1 (2)").Range("q" & j)
Set rngName = Sheets("Sheet1 (2)").Range("q" & j)
If rng1.Value = rng2.Value Then
If rng1.Offset(0, 2).Value <> rng2.Offset(0, 2).Value Then
MsgBox ("Not equal " & rng1 & " Net " & rng1.Offset(0, 2) - rng2.Offset(0, 2))
Exit For
End If
End If
Set rng2 = Nothing
Next j
Set rng1 = Nothing
Next i`
Honestly, this is beyond my current skill level in VBA, and I can't think of any way to use the Macro recorder to help. I want to know if there is any way to optimize this code to run faster, and also if there is a way to adapt it to write out all ID numbers with the amount of variance, instead of displaying the message box for each ID number individually.
Thanks!

Answer 1

If the data is sorted (assumes ID in column Q, quantity in Column R):
Dim ErrorList as String
With Sheets("Sheet1 (2)")
For i = 1 To .Range("q" & Rows.Count).End(xlUp).Row step 2
if .range("R" & i).value <> .range("R" & i+1) then
ErrorList = ErrorList & "ID: " & .range("Q" & I) & " Net: " & _
.range("R" & i).value - .range("R" & i+1).value & vbcrlf
end if
next
end with
'do something like MsgBox with ErrorList
If the data is NOT sorted (same column assumptions):
Dim ErrorList as String
With Sheets("Sheet1 (2)")
For i = 1 To .Range("q" & Rows.Count).End(xlUp).Row
'assume .range("q"
Set Rng = .Range("q:q").Find(what:=.range("q" & i), LookIn:=xlValues, _
lookat:=xlPart, MatchCase:=False)
If .range("Q" & I).value <> rng.cells(1,1).value then
ErrorList = ErrorList & "ID: " & .range("Q" & I) & " Net: " & _
.range("R" & i).value - .range("R" & i+1).value & vbcrlf
end if
next
end with
'do something like MsgBox with ErrorList
The .Find is MUCH quicker than an inner loop through all the rows of data again (someone a week or so ago tested and found something along the lines of 1000x times faster than a loop). Unfortunately, this method will leave you with duplicate IDs in your mismatch list, since it will run through the whole list, finding each of the pairs and discovering that they both don't match:
ID Value
ABC 1
BCD 6
ABC 2
It will loop to ABC/1, find ABC/2, then later in the loop find ABC/2 and discover that it doesn't match ABC/1, and report on both. The sorted data in the first option will work better if you can get your data sorted.
NOTE: No code was tested in the writing of this answer. There may be typos to resolve

Answer 2

You can do this with a formula if there can be at most only two matches: eg if ID is in ColA and Amount in ColB then in ColC enter
=IFERROR(VLOOKUP(A2,A3:B$9,2,FALSE)-B2,0)
and fill down. Result will be zero if no mismatch (or no matching Id), otherwise will be the difference between the two amounts.