Passing Spreadsheet Ranges to VBA LINEST function

[TechMann]

I am writing a VBA function which will take X and Y curve points and determine their polynomial trendline coefficients. I don't want to create an Excel chart to obtain the coefficients.

Eventually I'd like to let the user select a set of X and Y points on a spreadsheet, pass them to the VBA function and return different values back to the spreadsheet.

J-Walk & Associates webpage provides equations for calculating the trendline coefficients. Unforturnately, I can't get the function to work.

Here is the primary code which is causing the problem.

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When I run the code above I get the error "Type mismatch". I tried converting the xFlow and yTDH values to an array but with no success.

Thanks in advance.

[protonLeah]

Post a workbook with some data so we can step through the code.

[TechMann]

I believe I did attach the file "Excel Trendlines Test.xlsm". It appears on the webpage when I view the post.