Filter numbers or characters from sting

Public Function NumberOrNoNumber(StrToCheck As String, Numbers As Boolean, Optional NumericTextTarget As TextBox, Optional TextualTextTarget As TextBox)
'example:
'    txtFilter = NumberOrNoNumber(txtStringIncludingNumbers, False, txtNumber, txtNoNumber)
'    txtFilter = NumberOrNoNumber(txtStringIncludingNumbers, True)
Dim Nstr As String 'targetstring for al numbers
Dim Tstr As String 'targetstring for everything exept numbers
Dim i As Integer
  For i = 1 To Len(StrToCheck)
    If IsNumeric(Mid(StrToCheck, i, 1)) Then Nstr = Nstr & Mid(StrToCheck, i, 1) Else Tstr = Tstr & Mid(StrToCheck, i, 1)
  Next
If Numbers Then NumberOrNoNumber = Nstr Else NumberOrNoNumber = Tstr
On Error Resume Next
NumericTextTarget = Nstr 'optional target for the numbers filtered out
TextualTextTarget = Tstr 'optional target for the text filtered out
End Function