Put 1 as value of the next column for every first time a value appears on the adjacent column

[Zedrick13]

Please help me with coming up with a formula so that the value "1" appears on the corresponding row of a column for every first instance a code appears on another column. Like this:

         A        B
1    GL23      1
2    GL45      1
3    GL45        
4    GL50      1
5    GL23        
6    GL23        
7    GL45       
8    GL51      1

So, like in the example above, I want the value "1" appear on the next column (Column B) whenever a code appears for the first time in Column A.

Thanks in advance!

 

[oldbrewer]

23	1
45	1
45
50	1
23
23				formula in B1
45
51	1			=IF(COUNTIF($A$1:A1,A1)=1,1,"")

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[Zedrick13]

Thank you very much, oldbrewer!

23	1
45	1
45
50	1
23
23				formula in B1
45
51	1			=IF(COUNTIF($A$1:A1,A1)=1,1,"")

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</tbody>

 

[oldbrewer]

this 73 year old man needs to exercise his brain and likes helping people on here..........