Visual Basic, Insert a column into Excel

I writing a VB program that inserts a column of cells into an existing Excel worksheet with a specified range (e.g. “A1:A20”). After the column is inserted, each cell up to row 20 is filled with a text string.
How can I insert a column of cells without specifying the range? In other words, I would like to fill each cell in the new column and stop when it reaches the last row of data in the other existing columns. Any help is appreciated!
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‘specify a range of cells and fill with text
Selection.Insert
Range(“A1:A20”).Value = “MY TEXT”
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