Dear Glenn,

Apologize for late reply.

in my computer, its taking 15s to calculate. please find my answer to your question.

One thought. Is there a possibility of having the raw data for each day in a separate FILE and having one summary FILE drawing in the slope & Intercept??

--->we would like to have one workbook to have easy review and approval.

So. Does it work?

---> it wont work.

Is there a possibility to divide the data up over multiple files?

--->we would like to have one workbook to have easy review and approval.

Looking forward to final sheet.

thanks for support.