Text MC will be the same setup as a generic text field - so your URL button will be something like:
API_EditRecord&rid=___&_fid_10=OPTION
Where 10 is the field ID of your dropdown. The only catch with a multiple choice field is that you have to provide a valid option in the dropdown if you have it set so you can't add new options.
Qrew Legendvikas
Here is an example of a formula URL button to set the value of a field and refresh the page.
var text Approve = URLRoot() & "db/" & Dbid() & "?act=API_EditRecord&rid=" & [Record ID#]
& "&_fid_99=" & URLEncode("Order Approved"); // change the 99 to the field ID# of the Multiple choice field field
var text RefreshPage = URLRoot() & "db/" & Dbid() & "?a=doredirect&z=" & Rurl();
$Approve
& "&rdr=" & URLEncode($RefreshPage)
