Auto-insert same value each Monday in cashflow worksheet?
 

This will seem like kindergarten to some of you...
While constructing an Excel worksheet as a simple cashflow aid, I would like
to tell the sheet that on each Monday, for example, when a category has no
value (0 in cell), a standard value should be inserted throughout the year.
eg Insert the same value every Monday against "income".
Also, can anyone direct me to a good list of formulae and some explanations
for a bear of little brain?