Rdlc Report Sum #Error in column

Question

Dear all coder please help me with this, I am having a column of student marks in my report and the row of the columns contains both Number as mark and Text as Grade. So when I sum the total of the column it throws an error #Error, where as when I replaced the Text or grade from the row as a number then it gives the correct result. But I want it to give the sum even when it contains the Text in the row, it should only calculate the Number and avoid Text. 

Please Help Me!!

 In the above picture it show #Error because I have Text in the number field, but I want it to be as it is but should avoid calculating when its not a number.

 

 where as when I replaced the Text or grade from the row as a number then it gives the correct result. But I want it to give the sum even when it contains the Text in the row, it should only calculate the Number and avoid Text.