A couple of suggestions:
1. Don't open up the Excel file on every iteration of the outer while loop. Only do it once since you are using the same file on every iteration. Move the Open nodes ahead of the loop, and the Close node after the loop.
2. You have a weird construction of bundling up references in a cluster, then immediately unbundling them. While I think I understand that you are trying to neaten up the wiring a bit, the immediate bundling and unbundling just seems like needless operations. I would recommend eliminating all of that.
3. You have a lot of local variables. That can lead to race conditions. Some are just redundant. I would eliminate the locals and replace them with wires wherever you can. For instance, you have 40 instances of "Exl- tbl-Exl", one in each of your cases inside the inner while loop. Meanwhile you have the terminal for that control unused in the while loop. Just wire from that terminal into the case structure through a tunnel, and you'll have access to the data in that control without the 40 instances of the local variable.
