Using Grand Totals of 2 pivot tables in a formula.

I have 2 pivot tables that have the same column names and I would like to be able to sum the grand totals for each column. eg. Table 1 has 3 columns: Div 1 - Div 2 - Div 3 and Table 2 has 3 columns: Div 1 - Div 2 - Div 3. I need the add the grand total of Table 1-Div 1 to Table 2-Div1 and display elsewhere on the sheet (M:30 for example). The size of each table changes depending on what is selected by the slicer for each one so I am not sure how to do this. Thanks for any help.