If there is a relationship matching by custid between the two tables, Go To Related Records can open the new window with the selected layout with a found set of all records with the same custid as the current record in the first window.
If there is no relationship, you can still do it if you use a script similar to this:
Set Variable [$CustID ; value: LayoutTable1::custid //use your names in place of mine ]
Go to layout
enter find mode
Set Error capture [on]
Set field [Layouttable2::custID ; $CustID ]