If you have the data in a text/CSV file then you can try: Data > Import External Data > Import Data This launches a wizard which lets you specify specific columns as text and that causes symbols like +, - etc not to be parsed by Excel
In VBA this can be done through the Worksheet("foo").QueryTables.Add method. There are quite a few options but the TextFileColumnDataTypes property lets you specify which columns to treat as text. It might be easier to work out what is happening by recording a macro of the wizard being used and then editing that to suit
If you're reading in the data more directly (e.g. via ADO or DAO) then just make sure the destination cell is in text format before the data is added
Worksheet("foo").Cells(r, c).NumberFormat = "@"
NB in your original solution, you almost certainly wanted to look at C.Formula rather than C.Value If a cell C had a formula of =123+456 then C.Value would be 579 whereas C.Formula would be =123+456
+1 on using the built-in Replace method in this context