I presume that you are aware that if you use the native Report Link field, that will be the default behaviour that you want, and I assume though that you are trying though to have a fancier Rich text formula field to replicate the same behaviour.
If you have a relationship you can have a summary field to count the # of children.​
You can also have a summary field of the [Maximum Record ID#] of children. of course, if these is only 1 child, then it will be the maximum.
so then you just have an IF
IF([# children] = 1,
URLRoot() & "db/" & [_DBID_INVOICES] & "?a=dr&rid=" & [Maximum Record ID#],
​
URLRoot() & "db/" & [_DBID_INVOICES] & "?a=q&query=" & "{'6'.TV.'" & [Record ID#] & "'}"​)
you will want to suppress the button in form rules or calculate to null if [# of children] = 0
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Mark Shnier (YQC)
Quick Base Solution Provider
Your Quick Base Coach
http://QuickBaseCoach.commark.shnier@gmail.com
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