I was wondering how you can use a range for a loop start and end positions.

Give a range B3:B25

I wouldlike to loop through each cell and if there exists a value (any
number including zero) then replace the value with the associated formula ...
in this case if B3, B17 and B23 were numbers then

B3 becomes =sum(C3:H3)
B17 becomes =sum(C17:H17)
B23 becomes =sum(C23:H23)

Also can variables be used as cell references

dfrank = C17
B17 becomes =sum(dfrank:H17)

thanks