when to use file extension and when not

[lastnn30]

Hello, I opened a new file and typed these 2 macros. The first one works the second one the second line does not. It seems I can not use Workbooks("book2")
However; if I change the second line to

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The main file I opened is not saved yet. Does that mean if a file saved then I have to use file extension when I call it, for example books2.xlsx ? and if the file is not saved yet, I can call it using the file name without extension, for example book1 ?

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[dangelor]

Does that mean if a file saved then I have to use file extension when I call it, for example books2.xlsx ? and if the file is not saved yet, I can call it using the file name without extension, for example book1 ?

Sounds right. The way around this is to assign the workbook to a variable when it's created. Something like:

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[romperstomper]

Yes, you should always use the file extension (if there is one) with the Workbooks property.