There is not a straightforward way in Axure to refer to a specific row instance in a repeater. As you’ve discovered if you do something to one widget in a repeater, it is, well, repeated for every row. Blessing and a curse. Two common methods are to trigger a “hidden” event for a widget in your repeater, or mark row(s) and update the marked rows.
The “hidden event” method typically calls an otherwise unused event for a widget in the repeater (like OnMove or OnRotate) and that event has a condition to test a row identifier (like [[Item.index]] or [[Item.Name]]) against a “target value” (like a global variable or widget text) which in turn would call your intended event (like, “set panel state”). So, if you want to show the “afterchange” state only in row 3, you could set OnLoadVariable to “3” and instead of changing the state of your panel1 dp, you could move the dp by (0,0) thus not resulting in any actual move but triggering its OnMove event. Every row’s panel1 dp will fire OnMove, and if the condition is true (like, If [[Item.index]] equals value of [[OnLoadVariable]]) then this must be the correct row (if false it gets skipped) and THEN the dp can change its own state which would only affect that row and no others.
The “mark and update rows” method requires a dedicated column in your repeater dataset (like, “panel1State”) and a condition in the OnItemLoad event that changes something in your repeater (like, If [[Item.panel1State]] equals value of "after" Set state of panel1 to afterchange). Then you can mark one or more rows, typically from some user action within the repeater (like, Mark Rows This in MyRepeater) and then update the marked rows, setting the “panel1State” column value to “after” which in turn would trigger the condition in the OnItemLoad to change the dynamic panel state only in rows which are marked.
If none of this is making sense, don’t worry, repeaters are kind of tricky. If you can post your .rp file it will be easier for forum users to modify it and demonstrate a solution.
Here are a few recent threads that could help you: