VBA invalid qualifier with string.copy - vba

Question

I'm writing a code that loops through the textboxes of a word document. These textboxes contain a picture and a caption. So far, I have written a code that gets the caption from the textbox (which I checked through MsgBox caption).
I want to copy the caption, clear the textbox of all content, and then paste the old caption back in (because I'm trying to replace the pictures with an updated one). However, I keep getting an error with caption.Copy and have no idea why. It says that caption is an "Invalid Qualifier." I did some digging around online but haven't solved my problem.
This was the most-related thing I found: Invalid Qualifier error in Visual Basic 6.0
Anyway, here's my code. Any help would be appreciated!
Sub ReplaceImages()
Dim str As String
Dim captionTag As String
Dim imageTag As String
'Dim objShape As Variant Type Mismatch?
Dim fileName As String
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.EnableEvents = False
'Select directory to match .PNG to figure in document
Set SelectFolder = Application.FileDialog(msoFileDialogFolderPicker)
With SelectFolder
.Title = "Select Directory"
.AllowMultiSelect = False
If .Show <> -1 Then GoTo ResetSettings
sPath = .SelectedItems(1) & "\"
End With
sFile = Dir(sPath & "*png")
Do While sFile <> ""
fileName = sFile
MsgBox fileName
imageTag = BetweenParentheses(fileName)
For Each objShape In ActiveDocument.Shapes
If objShape.Type = msoTextBox Then
Set shapePicture = objShape
str = objShape.TextFrame.TextRange.Text
If InStr(str, "(") > 0 Then
captionTag = BetweenParentheses(objShape.TextFrame.TextRange)
If captionTag = imageTag Then
If InStr(str, "Figure") > 0 Then
Dim firstTerm As String
Dim secondTerm As String
Dim caption As String
firstTerm = "F"
secondTerm = ")"
Dim startPos As Long
Dim stopPos As Long
Dim nextPosition As Long
nextPosition = 1
caption = objShape.TextFrame.TextRange.Text
Do Until nextPosition = 0
startPos = InStr(nextPosition, caption, firstTerm, vbTextCompare) - 1
stopPos = InStr(startPos, caption, secondTerm, vbTextCompare) + 1
caption = Mid$(caption, startPos + Len(firstTerm), stopPos - startPos - Len(firstTerm))
nextPosition = InStr(stopPos, caption, firstTerm, vbTextCompare)
Loop
caption.Copy 'This is where the error is
End If
End If
End If
End If
Next objShape
sFile = Dir
Loop
ResetSettings:
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.EnableEvents = False

Answer 1

The caption variable is a string while the Copy method only applies to objects in the Word object model.
You store the text from the TextFrame into the caption variable:
caption = objShape.TextFrame.TextRange.Text
And then manipulate it inside your loop.
If you want to keep the value of the caption variable, then assign the value to another variable:
Dim someOtherVariable As String
someOtherVariable = caption

Answer 2

There might be some different between Excel and Word VBA in embedded shapes, but the following should be easy enough to adopt to word:
Sub test()
Dim shp As Shape, s As String
Set shp = ActiveSheet.Shapes(1)
s = shp.TextFrame2.TextRange.Text ' this is a string which doesn't have a Copy method
Debug.Print s
'but:
shp.TextFrame2.TextRange.Copy 'copies to clipboard!
End Sub
You can double check that the text is in the clipboard by pasting it directly into the immediate window (or wherever).