AutoHotKey Loop through rows and columns

I would like to loop through columns in Excel via AHK script.

XL := ComObjActive("Excel.Application")
Columns := Object(1,"A",2,"B",3,"C",4,"D",5,"E",6,"F",7,"G",8,"H",9,"I",10,"J",11,"K",12,"L",13,"M",14,"N",15,"O",16,"P",17,"Q")
For Keys, Value In Columns
Row := 3
Loop, 10
{
    XL.Range(????? . Row). Value := "Test" A_Index
}

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I'm having trouble with the how to call the column and loop to the next column. The goal in the end is to copy cells one at a time and assign a variable to each cell in a row and then loop through that on the following row.

So...
ColumnLoop
B3 Copy to clipboard Paste to Variable appended with A3
C3 Copy to clipboard Paste to Variable appended with A3
through to Column H
RowLoop
Should do the same as above but on Row 4