Hi Davefin,
I assume that you are trying to save the value returned by the function you are using to the Excel column.
However, I am afraid that it won’t return the proper value by this way.
Please consider to use a Compose function to get the value first, then use the output of the Compose action for the corresponding field of the action “Insert row”.
You may try to create the flow to something likes below:

Please try it on your side and feel free reply if you need more help.
Best regards,
Mabel Mao