How to NOT update a formula

[Gringoire]

Hello guys,
Imagine I have a cell C1 with a formula =A1+B1

My need is to keep the value of C1 unchanged even after the value in A1 is changed. B1 instead must continue to be updated when changed
I know how to do that by VBA (passing the cell content by value and not by reference), but I would like to know if it is possible to achieve the same result without using VBA.

thanks in advance.

 

[bebo021999]

Reference to A1 but does not change if A1 change ?

Without VBA, the only formula I can make is:

C1=A1+B1-A1

 

[Gringoire]

I try to explain better:
The point is that a macro periodically copy and paste the value of C1 (just an example, situation is more complex) to a kind of historical archive on another worksheet.
If after some month the value of A1 is updated (it is a cost) the new C1 data from now on must use the new cost A1, but the old C1 data, still linked to A1 should not update the cost.

Of course modify the macro would be the best solution, but this macro is extremely confused and not written by me, so if there was a method to prevent Excel updating the references to A1 value (only), it would be great.