how to Sum last 10 values of a dynamic column excluding zero

hi, i have this formula =SUM(OFFSET(P2,MATCH(1E+30,P:P)-1,0,-10,1)) which
sums the last ten values in column P, i was hoping someone could amend it
slightly for me. As column P is dependent on other entries the entire column
has 0 in it which makes this formula ineffective, i can't put an IF formula
into column P because then that wrecks other formulas that need column P, so
i need to work in a way of excluding zero into the forumla above.

Also, the formula does not work until there are ten values in the column, is
there any way to make it work and count the values up until the column gets
ten entries?

thank you for your help!
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thanks