Timer , code to check IF worksheet is open else Close it. ??

Hello,

On my userform i have an OK button and a Refresh userform button , and an Userform initialize.
When somebody has entered all the data they press the OK button and it all the data enters on a worksheet. Then it closes.
Because of this..

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I also have a timer which closes it if there is no activity.

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And i have a Update refresh button.

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And last but not least , on initialize it opens the file again.

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The problem: Many times because of the timer or OK button it tries to close the file while there is no file open which gives an ERROR.
Or the person presses Update/refresh before the file is closed and then the userform initializes and tries to open the file again which causes the error , or popup : This file already open are you sure blablalbla.

Solution : A way to check if workbook is open else close it. I tried: If WorkbookIsOpen then Workbook(name.xls).close true
but cannot figure out how to do it.