totalizer with missing on daily basic

lechatchante  I have 2 thoughts on what you might want and have created a sample sheet (attached).

option 1: NET where the value is only shown when a data point exists and gives a result based on prior valid point.  Formula sample:

=IF(C2="","",MIN(C2:C$50)-MAX(C$1:C1))

option 2: EST (estimate) where the values inbetween are estimated based on the #days in between. sample formula:

=IF(ROW()=ROW($E$1)+1,C2,LET(prior,XMATCH(MAX(IF(ISNUMBER(C$1:C1),$A$1:$A1,0)),$A$1:$A1),next,XMATCH(MIN(IF(ISNUMBER(C2:C$50),$A2:$A$50,9E+99)),$A$1:$A$50),(INDEX(C$1:C$50, next)-INDEX(C$1:C$50, prior))/(next-prior)))