checking each character in a string

a string for example consists of "hdjh568djd"
i want to check every character in the string, if detected that character is not a value then exit the function.
seems like this is not the way to do it?
str="hdjh568djd"
For Each Char In str
If Val(Char) = 0 Then Exit For
Next

Code:

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 str = "hdjh568djd"
 
 For i = 1 To Len(str)
  If Val(Mid(str, i, 1)) = 0 Then Exit For
 Next

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thanks for the help...it works