VBA looping through files that meet two criteria - excel

Question

Below is working code that is looping through files in a folder based on a user's search criteria. The folder will grow throughout the year to over 1000 files, so rather than looping through all of them every time the macro runs, I would like to add a second criteria that compares the time stamps on the files to a time stamp saved on the file as the last time it was run. LastUpdateDate is set up as variable in date format at the top of the module, and the old timestamp is saved to it at the beginning of the code.
I tried this but it left me with a run time error. Is this doable using Do While, or is there another format I need to be looking at? I also tried nesting the date comparison as an if statement under the Do While, but came up with other errors.
Do While FileName <> "" and FileDateTime(FileName) > LastUpdateDate
Working code from this section:
FileName = Dir(FolderName & "*" & MyCriterion & "*" & ".xl??")
'Loop through all matching files
Do While FileName <> ""
'Open the next matching workbook
Workbooks.Open (FolderName & FileName)
Sheets("Report Data").Select
'Call GrabTheData
GrabTheData
'Close the workbook
Workbooks(FileName).Close savechanges:=False
'Get the name of the next match in folder
FileName = Dir
Loop
End Sub

Answer 1

Two things:
FileDateTime
FileDateTime requires the full file path, not just the file name
Loops and Conditions
Do While (condition) stops execution of the block when (condition) is no longer true.
That is, it will stop execution as soon as (condition) is false. I don't believe this is the intended behavior.
Put an If (condition) block within the loop itself. This will loop through every workbook that matches MyCriterion, but only operate on those that match (condition).
Example (with recommendations)
Sub GrabAllData(ByVal FolderName As String, ByVal MyCriterion As String)
Dim FileName As String
Dim LastUpdateDate As Date
Dim wb As Workbook
LastUpdateDate = ThisWorkbook.Worksheets("Parameters").Range("LastUpdateDate").Value 'Named Range called LastUpdateDate on sheet "Parameters" in ThisWorkbook
'Make sure FolderName ends in a backslash
If Right(FolderName, 1) <> "\" Then FolderName = FolderName & "\"
'Get matching files for MyCriterion
FileName = Dir(FolderName & "*" & MyCriterion & "*" & ".xl??")
'Loop through all matching files
Do While FileName <> ""
If FileDateTime(FolderName & FileName) > LastUpdateDate Then 'FileDateTime requires the full file path, not just the file name
'Open the next matching workbook - work with the workbook directly, rather than working with ActiveWorkbook, ActiveSheet and Selections
Set wb = Workbooks.Open(FileName:=FolderName & FileName, ReadOnly:=True)
'Call GrabTheData on the workbook
GrabTheData wb
'Close the workbook
wb.Close SaveChanges:=False
End If
'Get the name of the next match in folder
FileName = Dir
Loop
Set wb = Nothing
End Sub
Sub GrabTheData(ByRef wb As Workbook)
Dim wsOut As Worksheet, wsIn As Worksheet
Set wsOut = ThisWorkbook.Worksheets("Aggregated Data") 'Worksheet called "Aggregated Data" in ThisWorkbook
Set wsIn = wb.Worksheets("Report Data")
' ### Manipulate the data and write to wsOut, no need to work with Selections ###
End Sub