Employ the Columns property to work with columns. This property return a Range object that represents columns of range
In the ensuing example, Columns[1] returns column one of used range on Sheet1
Workbook.Sheets[1].UsedRange.Columns[1].Font.Bold := true;
The ensuing example clears contents of column three in the range B5:F19
Workbook.Sheets[1].Range['B5','F19'].Columns[3].ClearContents;
The ensuing example merges the first column of range B2:C5
Workbook.Sheets[1].RCRange[2, 2, 5, 3].Columns[1].Merge(False);