OK, if I understand, what you're saying is that you don't want action to be able to be taken on the second item in the Gallery before the first one is completed. If that is correct, then the following solution will work. You will just have to change the logical tests to match your fields.
For my example, I have a datasource (myList) with an order field (theOrder), a field for if the work is completed (isComplete).
In the arrow icon of your Gallery, edit the DisplayMode property to put a test of the completed items. For my mockup, that amounted to:
If(
First(
SortByColumns(
Filter(myList, isComplete = false),
"theOrder",
Ascending
)
).theOrder < ThisItem.theOrder,
DisplayMode.Disabled,
DisplayMode.Edit
)
So, what are we doing? I find it helpful to start at the inside and work out.
Filter() -- gets the return of records that are not marked as completed
SortByColumns() -- puts those records in an ascending order, so that the one we want to require to be the first one worked on is, in fact, the first in the returned set
First() -- gets that first record that should be worked on (the first one not marked as complete)
First().theOrder -- gets us the data in the sorting field so that we can compare it against our records. Only if ThisItem's sort field is equal to or less than will the DisplayMode of the button be "Edit." Put another way, if the sorted field is greater than the record that they SHOULD be working on, they WON'T be able to work on it, because the button will be disabled.
CAVEAT:
The result of this is that ANY work order at or below the current work order's sort value will have a button available. So when the user should be working on the first work order, that will be the only one with a visible/enabled button. When the first work order is marked as "completed" and the user can move on to the second work order, BOTH the first and the second work order will have the arrow icons. If you would prefer that the user is only allowed to work on the current work order (and not revisit previous work orders marked as Completed), change the less-than operator to an equals operator, and reverse the Disabled/Edit portions of the If() statement.
In that case, you should consider a way to let the user edit a previously completed work order to correct some mistake (if that is allowed by whatever other governance guiding your development). For example, you could alter the color of the arrow icon based on whether the work order was marked as "completed" or not.
If(ThisItem.isComplete, orange, black)
That way, only the latest work order to become available to the user would have an arrow of one color, while all other arrows for the completed work orders would be of a different color. If the process would be different for editing a completed item versus editing an in-process item, you'd add an If() statement in the OnSelect event of the arrow icon.
