[ms-xlsx]: Excel (. xlsx) Extensions to the Office Open xml spreadsheetml file Format

dx: An unsignedInt ([XMLSCHEMA2] section 3.3.22) attribute that specifies the width of the scroll bar in pixels. This attribute only applies to list boxes, scroll bars, spin boxes and drop-downs<17>.

firstButton: A Boolean ([XMLSCHEMA2] section 3.2.2) attribute that specifies whether the object is the first button in a set of radio buttons. This attribute only applies to radio button form controls.

Value	Meaning
"true"	The object is the first button in a set of radio buttons.
"false"	The object is not the first button in a set of radio buttons.

fmlaGroup: An ST_Formula ([ISO/IEC29500-1:2011] section 18.18.35) attribute that specifies the cell an object in a group box is linked to. This attribute overrides the attribute fmlaLink for any radio buttons within a group box. This attribute only applies to group box form controls. The application can chose to remove and not save this element and use the attribute fmlaLink of the first radio button in the group. This attribute MUST be a cell reference (see [ISO/IEC29500-1:2011] section 18.17.2.3).