How to convert text(with html tag) to XML -WordprocessingML?

I have a string variable. I want to convert it in WordprocessingML(kind of XML). I can convert if I have only string variable(static string) but everytime value of string variable is different. I have tried by didn't get any logical idea.

Example:

Dim strData As String
strData = "This is Bold Text. This is Italic Text"

WordprocessingML (kind of XML) conversation:

"1.0"?>
"Word.Document"?>
xmlns:w="http://schemas.microsoft.com/office/word/2003/wordml"
xml:space="preserve">
This is
Bold
Text. This is
"on"/>
Italic
Text

In my case, `strData` can be any string which can have HTML tags for formatting.

Ex:

strData = "This is Bold Text. This is Italic Text"
strData = "This is Bold Text. This is Italic Text"
strData = "This is Bold Text."
strData = "This is Bold."

I have tried to use Replace function but it doesn't work in all cases.

Can anybody suggest me how to convert any string in this kind of format?