locking information in a cell
 

I have set up several spreadsheets with links to another sheet. I want individual cells to be filled with information from the other sheet, but once the value is there, I want that value to stay there and not change when the linked cell in the other sheet changes. In other words, sheet A has a price, which I have linked to a column in sheets B,C,D,and E. When I add ingredients on those sheets, the price from sheet A appears in the column. Because there is a formula, though, whenever I change the price on Sheet A, the prices already entered on those sheets change. I do not want this to happen. Instead, I want the prices, once entered on the sheet, to stay the same ( the price changes weekly). Is there a way to do this?