URL Formula to open a form in a different app

I am trying to create a button in a one app that will open a form in a different app and return me to the original app when complete.  The form is intended to create a new record in the app where the form is located.

At the moment I have
URLRoot() & "db/" & [bqdfx9d5f] & "?a=API_GenAddRecordForm$_fid_2=" & URLEncode([Project Number]) & "&z=" &Rurl()

bqdfx9d5f was the table dbid from the app information.  

This is my first attempt at a URL formula and the more challenging of the formulas on my todo list for today.  The other URL formulas are staying in the same app.

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Paul Peterson
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