Expression calculating values of cells not blank

[AlfSam]

((I want to calculate an entry fee [Column1 (text)] * constant (e.g. $25) only if Column1 is not blank) then add value [+] to next calculation [Column2 (text)]* constant [+] [Column3] * constant ) show sum total $ for up to 4 entries.
calculation would be $0 when cell blank (i.e. no entry).
Can someone suggest how the expression would be written in the expression builder?

[Bob Fitz]

In a blank column of a query, perhaps something like:
ColTots:CCur((Nz([Column1],0)*[Constant])+(Nz([Column2],0)*[Constant])+(Nz([Column3],0)*[Constant]))

I am assuming that Constant is the name of a column (field). Column1, Column2 and Column3 would need to be replaced with your real field names.
The names used, suggest that the database has not been normalised correctly.