How to stop cell's new value impact a formula result

in A1 I have minutes (e.g 26), in B1 I have seconds (e.g 111). I want to keep seconds less than 60 in B1 and convert all 60 seconds to minute and add to A1. So I typed in A1 :
= 26+QUOTIENT(B1, 60)
It got value 27. Good. Then I typed in B1 :
= MOD(B1, 60)
It got value 51. Good. But as B1 value changed, A1 value also changed. Considering that, I will create new rows subsequently with corresponding values to minutes and seconds and will like to apply this process to them as well, what can I do? Is the only way manually to do the process (to write the QUOTIENT formula in appropriate row in A column and then strip off the formula and turn the cell's content into just value to prevent being impacted by B column cells' new values)?

why not just use 2 new columns, that way you preserve your original data?
c1=26+quotient(b1,60) or even c1=a1+quotient(b1,60)
d1=mod(b1,60)

I just want to know the capabilities of Excel.