Loop Macro Goes Past While / Until Parameter

I am running a macro to loop through a list of codes which takes the unique code, goes to a different spreadsheet, finds related data based on that code and if it meets certain criteria, and retursn the same code if it works. Pretty much a filtering process, but I have it returning the code because I do not want to do the calculations in the Macro itself.

Here is the code:

VB:
On Error Goto Label1
Do
Windows("Byron_MonthlyPDPWellList.xlsx").Activate
Range("A" & I).Select

[Code] .....

"I" begins at 2 and counts up until it reaches Count, which is the number of total rows in the column.

However, when I step through the code, it continues to loop through the code where "I > Count".

I have tried "Until I > Count", "Until I = Count", "While I <= Count". And none of them seem to work. It gets stuck in an endless loop cycle.