Visual Basic for Applications Reference
Returns a Variant of subtype Error containing an error number specified by the user.
The required errornumber argument is any valid error number.
Use the CVErr function to create user-defined errors in user-created procedures. For example, if you create a function that accepts several arguments and normally returns a string, you can have your function evaluate the input arguments to ensure they are within acceptable range. If they are not, it is likely your function will not return what you expect. In this event, CVErr allows you to return an error number that tells you what action to take.
Note that implicit conversion of an Error is not allowed. For example, you can't directly assign the return value of CVErr to a variable that is not a Variant. However, you can perform an explicit conversion (using CInt, CDbl, and so on) of the value returned by CVErr and assign that to a variable of the appropriate data type.