As part of a larger program, I ask users to enter a name for the
worksheet. I want to have in built in error checking to make sure
that if the user enters a blank, just numbers, special characters, or
anything else that would cause a name in naming a worksheet that it
will ask the user for a new name until they enter one that is valid.
This is the section of code that causes problems:

Public Function CheckSheet(newSheetName As String) As String
Dim ws As Worksheet

'Makes sure that the name is a valid name in Excel (not numeric,
special characters, or blank)
On Error GoTo ErrHandler:
Set Sheets(ws).Name = newSheetName

CheckSheet = newSheetName

ErrHandler:
MsgBox "Please enter a valid name.", vbInformation
newSheetName = InputBox("What would you like to name the new
week?", "Week Name")
Resume
On Error GoTo 0
End Function

I am not that familiar with using On Error and have looked at pretty
much all the how to's on the internet, but I can't figure out my
problem. I have also tried using it a number of other ways including
a while loop that tries to make use of the IsError function, but
everything I try gives me either an error message or an infinite
loop.

I think I am getting a type mismatch error when I try to set the sheet
name to the user defined (newSheetName) variable, but I'm not sure
why.

Any help is greatly appreciated!