XHeight usage

I am having some trouble implementing XHeight usage in my print routine

Mypic.graphics.DrawTextLine(mNote.Title, 100, 30,650, iOSTextAlignment.Left, True) ’ Left-aligned

Mypic.graphics.DrawTextBlock(mNote.Details, 100, 45,650,500, iOSTextAlignment.Left, True) ’ Left-aligned

How do I reference XHeight to locate my Textblock print location in relation to the Drawtextline?

I thought that the usage might be like this

Dim h As Double
h = iOSFont.XHeight

but it says iOSFont.XHeight doesn’t exist??

Dim h As Double
h = iOSFont(Arial).XHeight