[vb.net] VBA error 1004 - select method of range class failed

First time poster, so if there is any formatting, or guidelines I failed to adhere to, please let me know so that I can fix it.

So I am basically asking the user for the file directory of the excel file, then I setup some variables (originally set at public as project variables, since these were being used and changed in other places). I have also added the lines to set these variables to nothing (just in case, I do not think that it should matter). I then set these variables to the excel file, workbook, and sheets that I want to access.

Dim filepath as String
filePath = CStr(fileDialog)              'ask file dir, set to string
Dim sourceXL As Variant                  'these three were orig project variables
Dim sourceBook As Variant
Dim sourceSheet As Variant
Dim sourceSheetSum As Variant

Set sourceXL = Nothing                    'set to nothing in case...?
Set sourceBook = Nothing
Set sourceSheet = Nothing
Set sourceSheetSum = Nothing

Set sourceXL = Excel.Application          'set to the paths needed
Set sourceBook = sourceXL.Workbooks.Open(filePath)
Set sourceSheet = sourceBook.Sheets("Measurements")
Set sourceSheetSum = sourceBook.Sheets("Analysis Summary")

Dim measName As Variant                    'create variable to access later
Dim partName As Variant

sourceSheetSum.Range("C3").Select           'THIS IS THE PROBLEM LINE

measName = sourceSheetSum.Range(Selection, Selection.End(xlDown)).Value
sourceSheetSum.Range("D3").Select
partName = sourceSheetSum.Range(Selection, Selection.End(xlDown)).Value

So I created two different sheet variables 'sourceSheets' and 'sourceSheetsSum', the code works if i use 'sourceSheets', but error 1004 occurs if i use 'sourceSheetsSum'. I have also tried the code with the variable 'sourceSheet' removed completely, in case that was overriding 'sourceSheetSum' for some reason.

I am fairly confident that the excel workbook and sheets exist and are being called correctly, since I ran a quick bit of code to loop through all the sheets in the workbook and output the names, shown below.

For j = 1 To sourceBook.Sheets.Count
Debug.Print (Sheets(j).name)
Next j

With the debug output of

Measurements
Analysis Summary
Analysis Settings

So, does anyone have any ideas what this error could mean, or how I can possibly go about finding more about what the error actually is?

EDIT: So I decided to add a bit to the listing of the sheet names, not sure if it will help at all.

For j = 1 To sourceBook.Sheets.Count
    listSheet(j) = Sheets(j).name
Next j    
Debug.Print (listSheet(2))    
Set sourceSheetSum = sourceBook.Sheets(listSheet(2))

The debug prints Analysis Summary, so I know that the sheet exists in the workbook, and there should not be any issues with a 'typo' in the names.
The code still has the same error at the same line though.

deusxmach1na: I think you wanted me to change

Dim sourceXL As Variant                  
Dim sourceBook As Variant
Dim sourceSheet As Variant
Dim sourceSheetSum As Variant

Set sourceSheet = sourceBook.Sheets("Measurements")

To

Dim sourceXL As Excel.Application
Dim sourceBook As Excel.Workbook
Dim sourceSheet As Worksheet
Dim sourceSheetSum As Worksheet

Set sourceSheet = sourceBook.Worksheets("Measurements")

But this does not change the error, I remember I had it similar to that, and then changed it since I read that variant is like a catch all, not actually that solid on what variant is.

You can't select a range without having first selected the sheet it is in. Try to select the sheet first and see if you still get the problem:

sourceSheetSum.Select
sourceSheetSum.Range("C3").Select

Removing the range select before the copy worked for me. Thanks for the posts.

assylias and Head of Catering have already given your the reason why the error is occurring.

Now regarding what you are doing, from what I understand, you don't need to use Select at all

I guess you are doing this from VBA PowerPoint? If yes, then your code be rewritten as

Dim sourceXL As Object, sourceBook As Object
Dim sourceSheet As Object, sourceSheetSum As Object
Dim lRow As Long
Dim measName As Variant, partName As Variant
Dim filepath As String

filepath = CStr(FileDialog)

'~~> Establish an EXCEL application object
On Error Resume Next
Set sourceXL = GetObject(, "Excel.Application")

'~~> If not found then create new instance
If Err.Number <> 0 Then
    Set sourceXL = CreateObject("Excel.Application")
End If
Err.Clear
On Error GoTo 0

Set sourceBook = sourceXL.Workbooks.Open(filepath)
Set sourceSheet = sourceBook.Sheets("Measurements")
Set sourceSheetSum = sourceBook.Sheets("Analysis Summary")

lRow = sourceSheetSum.Range("C" & sourceSheetSum.Rows.Count).End(xlUp).Row
measName = sourceSheetSum.Range("C3:C" & lRow)

lRow = sourceSheetSum.Range("D" & sourceSheetSum.Rows.Count).End(xlUp).Row
partName = sourceSheetSum.Range("D3:D" & lRow)