How to search and replace a string in Excel Shape (textbox) using Powershell.

Question

I have been asked to write a PS script to search/replace a string when found in Excel Shapes when they are textboxes. I have seen lots of simplistic PS scripts and even I can do a "foreach" loop through all the Shapes on a Sheet and display the
Name of each Shape. But I have not found a property or method to expose the actual text in a textbox let alone change it.
I have seen vba script that does this as:  
Set xWs = Application.ActiveWorkbook.Worksheets(I)
For Each shp In xWs.Shapes
xValue = shp.TextFrame.Characters.Text
shp.TextFrame.Characters.Text = VBA.Replace(xValue, xFindStr, xReplace, 1)
Next
In Powershell, shp.TextFrame.Characters.Text is ignored and returns nothing.  It would be nice to know if this is possible in PS and if so, know how to do it and/or get an example to work from.  I would have thought that
PS and VB would use the same Excel object model but apparently they do not.
I am using Excel 14.0 and PS 3.
Any suggestions would be appreciated,
Michael

Answer 1

This didn't work for me.  I have the shape object and it shows the textframe property:
PS C:\> $shape | gm
   TypeName: System.__ComObject#{00024439-0000-0000-c000-000000000046}
Name                       MemberType Definition
Apply                      Method     void Apply ()
CanvasCropBottom           Method     void CanvasCropBottom (float)
SoftEdge                   Property   SoftEdgeFormat SoftEdge () {get}
TextEffect                 Property   TextEffectFormat TextEffect () {get}
TextFrame                  Property   TextFrame TextFrame () {get}
TextFrame2                 Property   TextFrame2 TextFrame2 () {get}
ThreeD                     Property   ThreeDFormat ThreeD () {get}
But trying to access it gives an error:
PS C:\> $shape.textframe | gm
gm : You must specify an object for the Get-Member cmdlet.
At line:1 char:20
+ $shape.textframe | gm
+                    ~~
    + CategoryInfo          : CloseError: (:) [Get-Member], InvalidOperationException
    + FullyQualifiedErrorId : NoObjectInGetMember,Microsoft.PowerShell.Commands.GetMemberCommand
PS C:\> $shape.TextFrame.Characters().text="hello"
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $shape.TextFrame.Characters().text="hello"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull
I hope this post has helped!