You'll have to use the actual API to generate the record. API_GenAddRecordForm is really just a way of pushing the user to the Add Record form and isn't meant to be used for automating the addition of records in the background. For this, you'll want to use API_AddRecord. Below is the code for a simple Add and Redirect:
var text tk = "your app token";
var text URL = URLRoot() & "db/" &
& "?a=API_EditRecord&apptoken=" & $tk & "&rid=" & [Record ID#] &
"&_FID_10=now" & //this would be your Date/Time Field
"&_FID_11=" & "Whatever value you want to put in Field 11"
"&rdr=" ;
var text Land = the URL where you want the user to land;
"<a class='Vibrant Success' & href=" &
$url &
URLEncode($land)
& ">Check In</a>"
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Blake Harrison
bharrison@datablender.io
DataBlender - Quickbase Solution Provider
Atlanta GA
404.800.1702 / http://datablender.io/
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