My problem so far is trying to combine data from separate sheets into one.

In other words, just an update without deleting prior data.

I have some code here that will shed some light;

  Private Sub copyDataFromCsvFileToSheet(parFileName As String, _
parDelimiter As String, parSheetName As String)

Dim Data As Variant  'Array for the file values

'Function call - the file is read into the array
Data = getDataFromFile(parFileName, parDelimiter)

'If the array isn't empty it is inserted into
'the sheet in one swift operation.
If Not isArrayEmpty(Data) Then
  'If you want to operate directly on the array,
  'you can leave out the following lines.
  With Sheets(parSheetName)
    'Delete any old content
   .Cells.ClearContents
    'A range gets the same dimensions as the array
    'and the array values are inserted in one operation.
    .Cells(1, 1).Resize(UBound(Data, 1), UBound(Data, 2)) = Data
  End With
End If
End Sub