Custom Excel VBA function returning error in some cases, not in other

Question

My function is supposed to check a cell for a string, and then return that string if its present, and return an empty string if it's not. The first two parts are working fine--it checks, and it returns the string it it's present, but if the string isn't present, it returns an error (#value). What's happening?

Function Keyword(cell As Range, word As String)
  'checks given cell for keyword, returns keyword if present
  If (WorksheetFunction.IsNumber(WorksheetFunction.Search(word, cell.Range("A1"), 1))) Then
     Keyword = word + ", "
  Else: Keyword = ""
  'returns empty string if not present
  End If
End Function

Call it like this: =Keyword(H2,"LED")

Answer 1

If the value you are looking for isn't found, you'll get run-time errors, and your function will fail. Easier to use InStr to search for the value:

If Instr(1, cell.Range("A1").Value, word, vbTextCompare) <> 0 Then Keyword = word & ", "