how to align text boxes in curve in powerpoint ?

You can highlight the text then, while it is highlighted, go to format and click on the drop down menu called, Text Effects. Once there, scroll down to the transform option and you should see a few choices for curved text/arching text.

See if this works:

xx = slide number with content placeholder

Dim oshp As Shape
'make view active
ActiveWindow.View.GotoSlide xx
'select a suitable placeholder
Set oshp = ActivePresentation.Slides(xx).Shapes(2)
'maybe do some checks here
'is it a placeholder eg
oshp.Select
'paste into
ActiveWindow.View.Paste

If you have 2007 you will also need to check the type of the placeholder.