replacing a variable name within a string with a value

[spooky]

Hi,

Select d_disb_amt from t_loan_disburse ment where n_loanacc_no = $LoanAccountNo$ and n_disb_no =$DisbNo$ ;

How do i replace the values within the '$ $' with a value, ie I want to convert it to

Select d_disb_amt from t_loan_disburse ment where n_loanacc_no = 640 and n_disb_no =1 ;

[spooky]

Hi,

This query is passed as a String , after replacing the variables within the it with true values I have to execute the same...

How do i get about this?