Text to Columns Problem

I have a column of stamp catalogue numbers which sometimes includes “subs” such as 111a, 222b, etc. So I select the column and apply the Text to Columns function. The sort is perfect and I save the file! However, if I add more catalogue numbers to the column I have to use the Text to Columns option again because the column has reverted to standard. Is this normal or am I doing something wrong? Thanks in advance.

That’s normal behaviour. T2C only works on the current data, it isn’t going to change any new data you enter.

Question: Why are you continuing to enter the new catalogue numbers in the old format?