Trying to find the correct syntax for a lookup function

I have a table that has eight rows of empty cells for building numbers. In the table below this is a pool of all the available building numbers. When one of our technicians completes a building I enter the building number in the top table as completed. I am trying to figure out how to write a formula that will automatically populate the bottom tale with the text "Completed" beside the building number they just entered in the top table. I hope I explained this well enough. Thanks for any help.

Maybe a checklist using IF(COUNTIF(?

checklist for freebird.xlsx

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