Element needs to be a variant, so you can't declare it as a string. Your function should accept a variant if it is a string though as long as you pass it ByVal.
Public Sub example()
Dim sArray(4) As string
Dim element As variant
For Each element In sArray
do_something (element)
Next element
End Sub
Sub do_something(ByVal e As String)
End Sub
The other option is to convert the variant to a string before passing it.
do_something CStr(element)