How To Suppress Macro Search-replace Warning When No Data Found

I have written a macro to convert data from a report exported from Salesforce.com to a format that is acceptable for upload to our website. One of the necessary conversions is to convert values from a Boolean value to a Y/N value. I wrote a macro with a series of search-replace commands such as this:

Code:
'replace 0s and 1s in "Direct Billing" column with appropriate data
Columns("R:R").Select
Selection.Replace What:="0", Replacement:="N", LookAt:=xlPart, _
SearchOrder:=xlByRows, MatchCase:=False, SearchFormat:=False, _
ReplaceFormat:=False
This code generates a warning when no "0" values are found:

"Microsoft Office Excel cannot find any data to replace. Check if your search formatting and criteria are defined correctly. If you are sure that matching data exists in this workbook, it may be on a protected sheet. Excel cannot replace data on a protected worksheet."