Digital Neurosurgery in Excel: How I Expanded a Legacy VBA System Without Touching Its Soul
Everyone in the IT world knows systems like these. They’ve been running for years, they are absolutely critical to the company, and their internal structure resembles the intricate mechanism of a Swiss watch. Every cell, formula, and macro is interconnected by a network of thousands of dependencies. Everyone knows they work, but no one dares to touch them for fear that one false move could bring it all crashing down.
Now, imagine a client comes to you with a seemingly simple task: “Please expand this system. We want to add 1,100 new fields to the existing 400.”
This was my exact assignment. I was faced with a massive, complex vehicle registration system based on Excel and VBA—a digital organism composed of over 60 files, each with 50 sheets and hundreds of unique references. My goal was to perform open-heart surgery on this system without disrupting its rhythm.
The Surgical Plan: First, Do No Harm
In projects like this, revolution is a straight path to disaster. My strategy had to be different: evolution. I knew the key was a methodical, almost surgical approach, where every step is thought out and tested.
Instead of modifying existing code, I wrote new macros that supported the expansion. Instead of manually changing thousands of formulas, I created a mechanism that dynamically generated new references only for the added fields, leaving the old system untouched.
Some of the work was incredibly repetitive, like creating dozens of new data files. This is where automation came to the rescue. I created small but clever automations in VBA that handled the tedious work for me, minimizing the risk of human error.
' A simple automation that generated 35 new files for me,
' creating a perfect copy with a new serial number.
Sub Create26_60()
For number = 26 To 60
'Open the previous file
Set oldFile = Workbooks.Open(folderPath & "Data_File-" & (number - 1) & ".xlsm")
'Save it as a new file
oldFile.SaveCopyAs folderPath & "Data_File-" & number & ".xlsm"
'Open the new file and update its unique ID
Set newFile = Workbooks.Open(folderPath & "Data_File-" & number & ".xlsm")
newFile.Sheets("Card No").Range("A5").Value = "Data_File-" & number
'... (further operations)
Next number
End Sub
Every change was implemented iteratively, tested, and secured with a backup. It was slow, precise work, but it was the only way to guarantee the safety of the entire system.
The Patient Survived and is Thriving: Project Results
The operation was a complete success. We not only achieved the goal but did so while maintaining the highest safety standards. The final numbers speak for themselves:
The system’s capacity increased by 73%, growing from 400 to 1,500 fields.
98% of the auxiliary processes related to the expansion were automated.
Most importantly: 100% compatibility and functionality were preserved. The old system worked exactly as before, unaware of its new, expanded capabilities.
This project is proof that even the most complex and “untouchable” systems can be effectively developed. The key isn’t bravado, but respect for the existing architecture, methodical planning, and a cautious approach that allows for adding new features while preserving the soul and stability of the original solution.
Do you have a similar, mission-critical system in your company that everyone is afraid to touch? Or has your Excel spreadsheet grown to a size that’s difficult to manage?
I invite you for a free consultation. Let’s talk about how we can safely expand your tools to serve you even better.
