Suppose i have a normal linear regression construct, like

Sales = Intercept + M1*X1 + M2*X2 + M3*X3

Suppose X1,X2,X3 are the statistically significant variables from the model. I want to create some sort of a simulator which says , for X% increase in X1, what is increase in Y, likewise for X% increase in X2, what is increase in Y, and so on...

I know that typically, what we do is keep X2,X3 at average and multiply M1*X1 (Let's say this X1 value is 10 in first case, and then X1 value is 11 in 2nd case,..so here we have between the 2 scenarios we have increased X1 by 10% and hence i can measure what happens to Y keeping all other variables constant/median/average?)

PLease let me know if this is the right way to interpret this and if i am framing the question correctly?

Thanks!