concatenate text boxes to find combined value and copy paste alternative value into wb

Try:

on error resume next
Sheets("Database").Cells(WorksheetFunction.Match(SearchString, Sheets("Database").Range("B1:B10"), 0), 51).Value = Letters.Browse.Value
on error goto 0

Instead - note you will get an error if the searchstring isn't found, the on error resume next just means the code will "skip" the error.