Combine a date table with another dimension table without a key

Hello,

I have two tables, Table A and Table B. Table A combines a dimension and a column of values. Table B is a single column of Week as a name. This name is manually defined periodically in an attached Excel. I then have a slicer for Table B. I'd like to combine Table A and Table B, with a row created for each Week, then Site and Value. In the report I'd like to get the Value dynamically depending on which weeks or groups of weeks I have selected. See below for example. How do you recommend I go about this? I'm not very advanced so any help is appreciated.

Table A

Table B

Desired Result Table