URL button to populate a field with the current user

Hi There,

I currently have a url button that populates a certain field with the user that last modified the record.  

I need some help to change it from the user the last modified the record to the current user that pushes the button.

is there anyway to modify the below for the above requirement?


var text URL = URLRoot() & "db/" & Dbid() & "?act=API_EditRecord&rid=" & [Record ID#]

& "&_fid_30=" & URLEncode([Last Modified By]);


"javascript:" &
"$.get('" & 
$URL & 
"',function(){" &
"location.reload(true);" &
"});"
& "void(0);"