Excel IF -eq "Something" write in next available blank space

I'm having a little trouble writing a formula that will populate the next available blank cell if statement is True.

If Column G equals "#Number" then write "This Equals #"... But I only want "This Equals #" on one cell, not all 4 (A1; A2; A3; A4). Also, if 'A1' already contains "Something" write on 'A2'

Columns: A; B; C; G

A:

=IF(G1="#1","This Equals 1",IF(G1="#3","This Equals 3",IF(G1="#5","This Equals 5",IF(G2="#1","This Equals 1",IF(G2="#3","This Equals 3",IF(G2="#5","This Equals 5",IF(G3="#1","This Equals 1",IF(G3="#3","This Equals 3",IF(G3="#5","This Equals 5",IF(G4="#1","This Equals 1",IF(G4="#3","This Equals 3",IF(G4="#5","This Equals 5"))))))))))))

B:

=IF(G1="#2","This Equals 2",IF(G1="#4","This Equals 4",IF(G1="#6","This Equals 6",IF(G2="#2","This Equals 2",IF(G2="#4","This Equals 4",IF(G2="#6","This Equals 6",IF(G3="#2","This Equals 2",IF(G3="#4","This Equals 4",IF(G3="#6","This Equals 6",IF(G4="#2","This Equals 2",IF(G4="#4","This Equals 4",IF(G4="#6","This Equals 6"))))))))))))

C:

=IF(G1="#7","This Equals 7",IF(G1="#8","This Equals 8",IF(G1="#9","This Equals 9",IF(G2="#7","This Equals 7",IF(G2="#8","This Equals 8",IF(G2="#9","This Equals 9",IF(G3="#7","This Equals 7",IF(G3="#8","This Equals 8",IF(G3="#9","This Equals 9",IF(G4="#7","This Equals 7",IF(G4="#8","This Equals 8",IF(G4="#9","This Equals 9"))))))))))))