Dear,
If there is change in material price (@ RM, SFG or FG) then definitely there will be a variance. It is possible to settle variance at the period end activities.
You can use MR21 / MR22 to input the new price/quantity for a given material. But that is not the proper way of making changes.
The standard process involves,
1: @ the beginning of the period you run standard cost estimate(usually for FGs) and release the estimate to update the price in MMR. you can run multiple cost estimates for same material for cost comparisons by changing quantity structures . once the cost estimate is released then it is fixed for that particular period and the same is valid until you do the next cost estimate and release. as per SAP only one cost estimate release is possible for one material for a given period.
2: once this happens, you can execute the regular production processes of GI, confirmations, GR etc. Mostly during these processes, it is very common that you will receive variances (at GI, or during confirmations etc.) But we always try to avoid these variance as far as possible.
3: And at the period end activities for production/process orders, we settle the variances to proper objects. (FI and to COPA for analysis purpose).
Actually your doubt looks bit confusing, can you explain what you are looking at.
Pavan