Using VLOOKUP and need to remove duplicate

[gpalmiere]

Big time follower first time poster to the Forum.

I am creating a Task List spreadsheet with multiple sheets. Each sheet represents a different project. On each sheet I show activity, due date, priority, assign to, completion date and complete check box. When the box is checked the row turns grey.

The front sheet of the book is a summary page that shows each sheet. I want it to only show those tasks that are not complete on the different project sheets. Everything works fine until I click the complete box and the summary sheet repeats the task. I understand the logic on how it works but was wondering am I using the wrong command or if there is a nested if I can use to prevent duplicates.

Command I am using - =IFERROR(T(VLOOKUP($A4,Administrative!$A10:$N21,7,0)),"No Open Tasks")

Results before click complete -

Complete transition of Mike to Part-Time Hours
Pini to Part Time Hours
Resissue Glenn Stock under correct name
Denis define parameters for MI contract to begin drafting documents
Uniform Email Signature block for emails

Result after two boxes are checked complete -

Resissue Glenn Stock under correct name
Resissue Glenn Stock under correct name
Resissue Glenn Stock under correct name
Denis define parameters for MI contract to begin drafting documents
Uniform Email Signature block for emails

The VLOOKUP is displaying the first positive match like it is supposed to but I want the results to only show three open tasks.

Any suggestions or directions are welcome.

Thanks