Probably you are using ActiveX Button. Try this:
Sheets("Sheet1").CommandButton1.Enabled = False '--->change sheet name as required
EDIT:
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For a Form control Button the following line
ActiveSheet.Shapes("Button 1").ControlFormat.Enabled = False
disables the button i.e. click event will no longer work but the appearance of the button does not change which gives an impression that the button is still active. So work around for that is to change the color of the text of the button as follows:
Sub disable_button_2()
Dim myshape As Shape: Set myshape = ThisWorkbook.Worksheets("Sheet1").Shapes("Button 2")
With myshape
.ControlFormat.Enabled = False '---> Disable the button
.TextFrame.Characters.Font.ColorIndex = 15 '---> Grey out button label
End With
End Sub
And to bring back button to its original state write:
Sub activate_button_2()
Dim myshape As Shape: Set myshape = ThisWorkbook.Worksheets("Sheet1").Shapes("Button 2")
With myshape
.ControlFormat.Enabled = True '---> Enable the button
.TextFrame.Characters.Font.ColorIndex = 1 '---> Highlight button label
End With
End Sub