You can get the copied value from clipboard(windows) using Tkinter
from Tkinter import Tk
clip = Tk()
variable_name = clip.selection_get(selection = "CLIPBOARD")
Reference: How do I copy a string to the clipboard on Windows using Python?
Now open the excel file
pyautogui.hotkey('win','r')
pyautogui.typewrite(<excel_file_location>)
pyautogui.hotkey('enter')
Now we can go to A1 cell first and then we can traverse to any cell we want
pyautogui.hotkey('ctrl','home') # traversing to A1
pyautogui.typewrite(['down'],interval=0.25) # going to A2
pyautogui.typewrite(['tab','tab',..13 times],interval=0.25) # going to N2
pyautogui.typewrite(variable_name,interval=0.25) # entering the copied value