I have the following formula in cell A2 in worksheet "MainSheet":

HLOOKUP("Weight",sheet1!A1:C10,5,FALSE)

I also have in "MainSheet" a cell that contain a list with the names of other worksheets; i.e., in cell A1 I can select "sheet1", "sheet2" or "sheet3".

I need the formula above to change the reference to "sheet1" to the worksheet I select in cell A1; in other words, the formula in A2 will change its reference depending on what I select in cell A1.

How can I do this?
Thanks.