Opens another workbook but doesn't activate it, ignores ScreenUpdating = False

I updated a .xls workbook to .xlsm. It automatically opens another workbook, Lookups.xlsx, containing a bunch of lookup tables used in numerous combo boxes and formulas.
When I open the 1st workbook, Lookups.xlsx becomes and remains the active workbook, even though the code does a ThisWorkbook.Activate. The same is true if I run Auto_Open manually. Here is the original code:

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I tried stepping through it with the debugger. It opens Lookups, but when I hit F8 for the next step, nothing happens because the Lookups window now has the focus. If I click the debug window to put the focus back there, and then hit F8, it activates ThisWorkbook as it should.

I suspected some kind of timing issue, so I changed the code to the following:

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This solved the activation issue, but it ignores ScreenUpdating = False. This was not the case in previous versions of Excel. Does 2007/2010/2013 ignore ScreenUpdating = False when opening another workbook?

I've presented two different issues here. It would be nice to know the answers to both, but I'd settle for either one

I suspect that "thisworkbook" refers to the workbook housing the macro.

try

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Thanks for the suggestion. Actually, it would be

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I tried it, but with the same results.

ScreenUpdating will be made True when first routine ends and before second routine is run. This is normal and same as previous versions.

Based on that clue, I tried the following adjustment

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but it also didn't work. It pauses for 1 second, but leaves Lookups as the active workbook.