Transaction Lines - Scripting Applied to and Applying Transactions

With saved searches you can use the Applied To Transaction and Applying Transaction to return the line-to-line relationship between transactions such as Purchase Orders and Vendor Bills.  Is there a way to do this in SuiteScript to return the actual line-specific relationship instead of just the header-level relationship.  For example:

Purchase Order 100
Line 1= Item: Item A, Qty: 50, Rate: 5.00, Amount: $250.00
Line 2= Item: Item B, Qty: 25, Rate: 2.00, Amount: $50.00

Vendor Bill 123
Line 1= Item: Item A, Qty: 50, Rate: 5.25, Amount: $262.50

Vendor Bill 456
Line 1= Item: Item B, Qty: 30, Rate: 2.00, Amount: $60.00

If I have a script on the purchase prder where I'm looping through the 2 lines of the PO, is there any way for me to get the value of Vendor Bill 123, Line 1 when I'm on Line 1 of the purchase order, and get the value of Vendor Bill 456, Line 1 when I'm on Line 2 of the purchase order?  I know I can run a search for the applying transactions, which will return both Vendor Bill 123 and Vendor Bill 456.  I'd like to be able to directly get the values of the exact vendor bill