URL button to populate a field with the current user

hmmm..that's what I thought, i tried that but it doesn't put anything into field 30. still blank

Are you saying that the button did work properly for the [Last Modified by].  Do you have application tokens disabled?

You can also try this, as this is the format I usually use myself for Userid field types.

& "&_fid_30=" & ToText(User());

correct - the button worked fine when it was [last modified by]

app tokens are enabled.

Does your full formula provide an app token?  Have you posted your full formula?

here's the full formula

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);"

OK, so there is no way that the formula can work if your app is requiring Application Tokens.  You need to either turn off the need for Application Tokens or else provide on in the formula by adding in a line like,


var text URL = URLRoot() & "db/" & Dbid() & "?act=API_EditRecord&rid=" & [Record ID#]
& "&apptoken=xcxcxcxcxcxcxcxcxcxcxcx"
& "&_fid_30=" & URLEncode([Last Modified By]);


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

ah...some reason app token on the home settings on the app was click on.  Thanks for all your help your first solution works just fine now.

so in the future if my app application tokens need to be turned on then adding this line will suffice?

& "&apptoken=xcxcxcxcxcxcxcxcxcxcxcx"

Well, yes, that Syntax, but I assume that you realize that you need to go to "Manage Application Tokens" and click the button to create an Application Token for your app to use in URL formuals. 

ie  "xcxcxcxcxcxcxcxcxcxcxcx"

will not be the one that works for you!