In the end I counted the number of lines and multiplyed that by a factor of 13. Here is the code if anybody else every needs this in the future:
I used the following API call. However this does not work with a TextBox you must use a Rich Edit Control for this to return the correct results.
Code:
Private Declare Function SendMessageAsLong Lib "user32" Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Private Const EM_GETLINECOUNT = 186
Code:
MsgBox "Height Of Excel TextBox = " & 13 * SendMessageAsLong(MyRichEditBox.hWnd, EM_GETLINECOUNT, 0, 0)