参考

VBAで数式を書く方法
- Powerpoint 2013 vba create Equation / Mathzone - Stack Overflow
- Powerpoint VBA 数式を書く - Powerpoint VBAを使おう!
数式を文字列で表現する方法
- Word の行形式の数式と数式オートコレクト - Office サポート
- UnicodeMath, A Nearly Plain-Text Encoding of Mathematics - Unicode Technical Notes

コード

Sub InsertEquation(left, top, str)
	ActiveSheet.Shapes.AddLabel(msoTextOrientationHorizontal, left, top, 0, 0).Select
	Application.CommandBars.ExecuteMso "InsertBuildingBlocksEquationsGallery"
	Selection.Text = str
	Selection.Font.Size = 24
	Selection.ShapeRange.TextFrame2.WordWrap = msoFalse
	Application.CommandBars.ExecuteMso "EquationProfessional"
End Sub

Sub Sample()
	InsertEquation 30, 40, "F(t)=\sum_(x=0)^(n-1) \of \begin f(x) e^(-\ii  2\pi tx/N) \end"
End Sub