SSRS Expressions to find max value

Hi,

We have populated avg values in individual tables.

suppose below is the avg values in my table

Table 01

10 

20  

Table 002

56

12

How can i find the max values between these two tables.

I referred using MAX(report items!textbox.value)

but it did not show any output.

How can we compare among st expression/report items an get the max values between them?

Please help