You also have an additional problem if this is or will be a database that is hosted over a network and more than one user may be selecting this at the same time. Their choices will interfere with each other and the Replace Field Contents step may clear a user's selection before they want it to be cleared and edit locks on records can keep selected records from being cleared when they should be.
I'd also use a global variable instead of a global field unless this is a very old version of FileMaker that you are using.
What you can do, is update a global variable (this works with a global field also) such that it becomes a list of selected expectations separated by return characters. Selecting a control set up to look and act like a check box (but isn't) to select an object adds it to the list. Clicking it again to clear the selection deletes the item from the list in the global variable.
Your user can then click to select multiple items without any interference from other users and they can click a button named "done" or somthing to start a script to take them back to the other layout where the script can loop through the values in the global variable's list.
Here's a sample Select/Deselect script example:
If [ IsEmpty ( FilterValues ( $$ExpectList ; EXPECTATIONS::__kp_expectations_id ) ) // item not selected, select it ]
Set Variable [ $$ExpectList ; List ( $$ExpectList ; EXPECTATIONS::__kp_expectations_id ) ]
#Item is already selected, clear it
Set Field [$$ExpectList ; ¶ & $$ExpectList & ¶ ]
Set Field [$$ExpectList ; Substitute ( $$ExpectList ; ¶ & EXPECTATIONS::__kp_expectations_id & ¶ ; ¶ ) ]
Set Field [$$ExpectList ; Middle ( $$ExpectList ; 2 ; Length ( $$ExpectList ) - 2 ) // strips off leading and trailing returns ]
You can then set up a rectangle object and Layout text with a conditional formatting as both a button to perform this script and with conditional formatting that hides/reveals the "x" or other layout text used to show that the user has selected that item.