Convert column from string of numbers to a subtotal on select statment
This is definitely not a good data model.

If you are stuck with it you could use

SELECT ID, 
       X.value('sum(/x/text())', 'FLOAT') as Value    
FROM YourView
CROSS APPLY (VALUES(CAST('&lt;x&gt;' + REPLACE(VALUE, ';', '&lt;/x&gt;&lt;x&gt;') + '&lt;/x&gt;' AS xml))) V(X)


Online Demo