Sorry for the confusion!
The image in my previous post shows what should be happening, i.e. clicking a Size disables ALL Lengths. I'll later add code that will enable individual Lengths based on which Size is selected. So, it's working fine.
However, when the UserForm contains a Control that doesn't support the GroupName property - CommandButton, Frame, in fact anything other than an OptionButton or CheckBox it would appear - then I get an error: "Object doesn't support this property or method".
So, what I'm after is a way to filter out all Controls, (For Each x In Me.Controls), so that I don't get the error.
In pigeon-VBA my code would be something like:
For Each x In Me.Controls(OptionButton)
...
or
For Each x In Me.Controls
If x.Type = OptionButton
...
or
For Each x In Me.Controls
If x.GroupName And If x.GroupName = "Buttons"
...
or
For Each x In Me.Controls
If x.Name [contains] Length
...
S