I currently have 2 columns for my database and I'm trying to return all values in column 1 that don't contain a certain value in column two:

ex: Column 1 has 9 digit random value, sometimes repeated. There are 4 different options for column 2; P1, P2, P3, P4. 

I'm trying to only display values in column 1 that don't have a value of P4 in column 2. If they don't have a P4, then I want them all to be displayed, but once a Column 1 value is associated with P4, I don't want any of the column 1 values displayed. This process will continue through all column 1 values until the only values displayed in column 1 are values that do not have a P4 column 2 value associated with them.