SQL Server Parsing Key Value from Text

Question

i am a novice programmer in sql.
I want to grab some key value pairs from the text in sql column
e.g.
some text[Key1=Val1]some text[Key2=Val2][Key3=Val3]some text
i want a function which takes Keyname as input & returns the value related with it if found.
GetValueFmKey('Key1') should return Val1 and like on.
Note: the specified values are in text it may have pre or post text exists.

Answer 1

The Final code which i used is:
CREATE FUNCTION [dbo].[GetValueFmKey]
@TextToParse Varchar(max),
-- Input Text to be Parsed
@ParsingKey Varchar(max)
-- The Key for which Value to be Parsed
RETURNS VARCHAR(max)
AS
BEGIN
DECLARE @ReturnParsedValue VARCHAR(max)
DECLARE @SemiParsedString VARCHAR(max)
DECLARE @StringFound INT
SET @StringFound =patindex ('%'+@ParsingKey+'%',@TextToParse)
-- IF KEY found in Input Then only Proceed
IF(@StringFound<>0)
BEGIN
SET @SemiParsedString= substring(@TextToParse,patindex ('%'+@ParsingKey+'%',@TextToParse),patindex('%]%',substring(@TextToParse,patindex ('%'+@ParsingKey+'%',@TextToParse)+1,len(@TextToParse)))) 
SET @ReturnParsedValue = substring(@SemiParsedString,patindex('%=%',@SemiParsedString)+1,len(@SemiParsedString))
END
-- ELSE SET RETURN Value to NULL
ELSE
BEGIN
SET @ReturnParsedValue = NULL
END
-- Return the result of the function
RETURN @ReturnParsedValue
END
As It only checks if Key is present in Input Text else it returns NULL.