How to add and minus values?

Question

hi,
 
I stuck with one query in sp. In my aspx page one Text box named txtMoney and two buttons
btnAdd and btnLess this records is saving to tblCash.
 
think cash is 10000 i mean sample..while adding 5000 then it should add to that remaining amount 10000+5000=15000.it should update if i click btnadd button..and update button is to less amount from tblCash table so whenever i place some money and if i click btnLess button it should be minus from total cash..
 
can any one help me to create sp..
thanks and regards..
 
column in tblCash
tblCash contains cCash column so i want to update this column while adding and less..can any one suggest me..
how to create stored procedure for this and call it to in aspx.cs page..can any one suggest me?

please help me..