OpenpyXL: Runtime Error 6 Overflow - vba

Question

I have a program utilizing openpyxl that opens two existing Excel files. One is a simple worksheet with data that needs to be copied into the other file, which is a workbook containing many worksheets and with VBA macros that use this copied data. When the VBA code runs, though, I get a Runtime Error 6 overflow. The strange thing is that if I manually copy all of the required cells into the workbook, the macros run without a hitch. But when this process is automated, even though the values in the cells are identical, this error pops up. Below is the code which transcribes the data from one worksheet to the other.
def transcribe_client_data_to_workbooks():
_active_sheet_index = 5
for client in set(cdict.values()):
report_path = r'C:\Program Files\Notepad++\reports' + '\\' +
string.replace(client,'/','-') + '_report.csv'
wb = openpyxl.load_workbook('Bucket-Asset Allocation Model.xlsm',
read_only = False, keep_vba = True)
ws = wb.active
with open(report_path, 'rU') as f:
reader = csv.reader(f)
for row_index, row in enumerate(reader):
for column_index, cell in enumerate(row):
column_letter = get_column_letter((column_index+1))
ws[column_letter+str(row_index+1)] = cell
f.close()
wb.save('C:\\Program Files\\Notepad++\\workbooks\\' +
string.replace(client,'/','-') + '_workbook.xlsm')
I don't understand why I would receive this error message when this data is automatically copied in, but not when I copy/paste manually. I open the same workbook template each iteration and then save it as a new one after the appropriate data has been copied over. For reference, here is the section of VBA code where the error occurs.
Do Until Sheets("Raw Data").Cells(crow, 1).Value = Empty
aNumber = Sheets("Raw Data").Cells(crow, 1).Value
ticker = Sheets("Raw Data").Cells(crow, 9).Value
security = Sheets("Raw Data").Cells(crow, 8).Value
mValue = Sheets("Raw Data").Cells(crow, 12).Value
bAmt = Sheets("Raw Data").Cells(crow, 18).Value
uGain = Sheets("Raw Data").Cells(crow, 20).Value
Do Until Sheets("Accounts").Cells(acrow, 1).Value = aNumber
acrow = acrow + 1
Loop
Specifically it occurs on the line that increments acrow:
acrow = acrow + 1
I tried changing acrow from an integer to a long, but that just causes the program to run indefinitely until I click or cancel it, at which point I receive Run-time error '1004', Application defined or object-defined error, on the line directly preceding the increment of acrow.
Any help would be appreciated, thanks!

Answer 1

John Coleman was correct about the location of the overflow. The issue was that I was writing aNumber as strings and aNumber was declared in the VBA as Variant type, which according to the docs can represent anything other than a fixed length string. I simply changed my strategy and wrote account numbers as integers which resolved the problem.