Expression. Error: The column 'Column1' of the table wasn't found. Details: Column1

[JamesRead]

I don't know how to solve this problem, please help me guys.

[ppm1]

You are referencing a column that no longer exists. Click through each of the Applied Steps and find the first one that gives an error. In the formula bar, correct the reference to [Column1] (or delete that step and redo it).

Pat