The code you've posted isn't anything like what one would use for populating a document from a dropdown content control selection. See, for example: [SOLVED] Dependent Drop Down Lists in Word (vbaexpress.com), where there is code that does much more than what you're asking.

See also:

Dependent Text Content Controls
https://www.msofficeforums.com/word-...html#post46903
and, for different elements from a selected item to be output to different content controls:
https://www.msofficeforums.com/word-...tml#post120392


Dependent Dropdown Content Controls
https://www.msofficeforums.com/word-...html#post77762
and, for multiple levels of dependency:
https://www.msofficeforums.com/word-...tml#post132696


Cascading Dropdown Content Controls
https://www.msofficeforums.com/word-...html#post94603


Content Control Conditional Formatting
https://www.msofficeforums.com/word-...html#post47254


Dropdown Content Control Population from Excel
https://www.msofficeforums.com/word-...html#post46287

Creating and Tallying Mutually-exclusive Checkboxes
https://www.msofficeforums.com/word-...html#post33489
https://www.msofficeforums.com/word-...tml#post107008


Adding a New Row to a Table:
https://www.msofficeforums.com/word-...html#post87989
https://www.msofficeforums.com/word-...html#post38461
https://www.msofficeforums.com/word-...tml#post145675

I note that your post title refers to 'multiselect'. Neither dropdown nor combobox content controls allow more than one item to be selected at a time.