Dimoverride

AutoCAD has a command named Dimoverride which can be used to apply one or several dimension variable settings to a group of dimensions.  These overrides take precedence over the dimension style used on the dimension.

To use dimoverrides, you must know the dimension variable name of the setting(s) you wish to apply.  The dimension variable name for the suffix is DIMPOST.

Select Dimoverride from the Dimension Menu.

Command: dimoverride
Dimension variable to override (or Clear to remove overrides): DIMPOST 5
Current value <> New value: <> DIA.5
Dimension variable to override: 5
Select objects: (select a dimension)
Select objects: 5

Respond to the prompts displayed as shown above. Use the keyboard to enter the items in bold.
5 means press ENTER.  All selected dimensions will be updated.

This override method can be applied to a tool bar button as shown below.