Custom error handling vba - vba

Question

I have a cell that is a brutal nested if and if error. I don't want to have to paste my vlookup 5 times in the formula. Instead, I'd like to have a macro check the errors. The special case is 0 or 1.
I wrote this function to get the value of the vlookup.
Public Function ValidateRealization(value As String)
Dim validate As String
If value = "#N/A" Or value = "#VALUE!" Or value or = "#REF!" Or value = "#DIV/0!" Or value = "#NUM!" Or value = "#NAME?" Or value = "#NULL!" Or value = "0" Or value = "1" Then
validate = ""
Else
validate = value
End If
ValidateRealization = validate
End Function
However, I know it can be improved for one when I set the value, the formatting as a percentage is overridden.
Is there a better way to do this? Maybe by getting the active cells range, and setting the value property?

Answer 1

You are bringing in a string and not a value, so the return is a string.
set the parameter as variant and test for error:
Public Function ValidateRealization(value) As Variant
Dim validate As Variant
If Not IsError(value) Then
If value = 0 Or value = 1 Then
validate = ""
Else
validate = value
End If
Else
validate = ""
End If
ValidateRealization = validate
End Function
Which can be simplified to:
Public Function ValidateRealization(value) As Variant
ValidateRealization = ""
If Not IsError(value) Then
If Not (value = 0 Or value = 1) Then
ValidateRealization = value
End If
End If
End Function

Answer 2

2 points: first, you have ervalue which is undefined. Go to the top of your module, and add the line Option Explicit. Then go "Tools" > "Options..." and tick "Require Variable Declaration".
Secondly: Why not accept a Variant instead of a String, and use IsError?
Public Function ValidateRealization(value As Variant) As Variant
If IsError(value) Or CStr(value) = "0" Or CStr(value) = "1" Then
ValidateRealization = ""
Else
ValidateRealization = value
End If
End Function
{EDIT} If you have converted your value to a String before passing it, then use Select Case
Public Function ValidateRealization(value As Variant) As Variant
If IsError(value) Then
ValidateRealization = ""
Else
Select Case CStr(value)
Case "#N/A", "#VALUE!", "#REF!", "#DIV/0!", "#NUM!", "#NAME?", "#NULL!", "0", "1"
ValidateRealization = ""
Case Else
ValidateRealization = value
End Select
End If
End Function