add button to spreadsheet to open form

I have created a spreadsheet with a user form and the form opens automatically when the spreadsheet is opened. Once the user completes the form and "submits" the data the form goes away and the data is entered on the worksheet. This works great, BUT- users have asked to open the form from the worksheet so that they can add additional information. I tried to add a "button" on the sheet that would allow them to open the form- but I can't get the button to work...anyone have any suggestions?

The click event for the button should be:

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Your aren't changing the size or position of the form that might be causing it to not show are you?