Using DATEVALUE() Excel Formula within VBA when adding Custom Data Validation

Hello, I wonder if it could be possible for someone to help me with an error I am receiving on the following part of my code, as I am trying to add some data validation to a range of cells through VBA that prevents users from entering a date that is not between 2 dates, and also weekends:

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The error received is "Run-time error ' 1004':Application-defined or object-defined error" and when I "debug" the ".AddType" section above is highlighted yellow.
If I remove the 2 "DATEVALUE()" parts of the "AND" formula the code works fine. Ultimately, I would like to be able to add my "StartDate" and "EndDate" variables within the "DATEVALUE()" parts of the "AND" formula.

Please can someone help . . . Thanks in advance.

I don't think you can structure it like that as you are trying to contain everything within one formula.

For selecting between values, you need formula1 for the start value and formula2 for end value:

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This approach should work - just build your validation with the formula1, formula2 etc syntax. I believe this should work but haven't tried it with your example.