Compare Two Workbooks and Highlight Differences

I need to compare column A from two separate workbooks and would like to hightlight the differences in each workbook. I only need to highlight the cell, not the entire row.

Attached are my two workbooks. The names of the workbooks will change each week along with the number of rows. The compare column will always be A.

I have attempted the attached code but it errors out and I do not know why. Any help would be appreciated.

I currently copy/paste the formula in column B each week but would really like to automate the process with VBA, which I believe can be done.