Add A Space Before Every Cell Value

I'm trying to automate the importing and processing of a fairly large formatted text file (~15000 lines) containing many tables of data. I've been refining this process for several months and recently was alerted to a problem. A few of my tables have widths greater than 255 characters (309 to be exact).

My process involves opening the text file in Excel then performing a .Copy on the Worksheet into ThisWorkbook, naming the sheet "Source". I then perform up to 66 separate parse operations on the various tables depending on which options a user selected from a form.

The problem is that I assumed that the Copy Method would simply make a duplicate of that sheet in ThisWorkbook. Instead, it seems to have truncated any columns that are longer than 255 characters, leaving me with partial data in a few tables.

My workaround was to perform a TextToColumns on the text file prior to the import such that it would simply split the data into columns that could be reassembled on the other side. In doing so, I seemed to have stripped a leading <space> from each cell which was apparently put there previously. This is causing a lot of problems for my formatting code which also uses TextToColumns to separate the tables into columns. The simplest solution seems to be trying to add the spaces back in, assuming there isn't a better way to import this data in the first place.

Just prior to copying the sheet into ThisWorkbook, I'm using the following code after the TextToColumns to add the space back in, but it's taking an awfully long time and causing a noticable time delay in processing my code and adding considerable size to the finished workbook it creates. If someone could recommend a better solution, either to the import process or to replace this God-awful loop, I'd appreciate it. Thanks.

Application. ScreenUpdating = False
For i = 1 To 65535
wkbk.Sheets(1).Cells(i,3).Formula = " " & wkbk.Sheets(1).Cells(i,1).Value
wkbk.Sheets(1).Cells(i,4).Formula = " " & wkbk.Sheets(1).Cells(i,2).Value
wkbk.Sheets(1).Cells(i,1).Formula = wkbk.Sheets(1).Cells(i,3).Value
wkbk.Sheets(1).Cells(i,2).Formula = wkbk.Sheets(1).Cells(i,4).Value
Next i
wkbk.Sheets(1).Range("C:D").ClearContents
Application.ScreenUpdating = True

Also, I don't know how long the actual file will be, so I'm almost forced to assume 65535...