デリミタが"-"だけならもっと簡単になるね

Sub test2()

Dim strArray() As String
Dim rtnStr As String

testStr = "000070-00100-01230"

strArray = Split(testStr, "-", , vbTextCompare)

For i = 0 To UBound(strArray)

rtnStr = rtnStr + Trim(str(Val(strArray(i))))

If(i <> UBound(strArray)) Then rtnStr = rtnStr + "-"
Next

End Sub

文字列で連結して返す必要なければsplitして数値変換でおわり