The coordinates of a range is a string that you can create dynamically. The simplest way to loop through your rows would be something like this:
repeat with thisRow from 1 to 10
tell application "Microsoft Excel"
set theRange to "A:" & thisRow & "Z:" & thisRow
set theValue to (get value of range theRange) as list
-- do something with the row's data
end tell
end repeat
Update per comments: To get the number of rows needing calculation, I wrote a subroutine ages ago to help with this. Be sure you have some kind of "key" column that is consistently populated (in other words, there are no skipped cells). This currently takes into account a header row since all of my spreadsheets have them:
on GetItemCount(KeyColumn)
set RowNumber to 1
set theText to "cSyoyodylg" -- dummy value
tell application "Microsoft Excel"
repeat until theText is ""
set RowNumber to RowNumber + 1
set theRange to KeyColumn & RowNumber & ":" & KeyColumn & RowNumber
set dataRange to range theRange of sheet 1
set theText to (get value of range theRange)
end repeat
end tell
set rowCount to RowNumber - 1
return rowCount
end GetItemCount
To use simply do this:
set lastRow to GetItemCount("A") of me
repeat with thisRow from 2 to lastRow + 1
-- go attack Excel
end repeat