And here is a slightly more sophisticated script that's closer to Excel's 'Trace Dependents':

Usage exactly the same. Clicked in cell A3 and then clicked the "Run" button.
Clicking cell B3 and "Run" gives this:

Numbers 3 only.
SG
tell application "Numbers"
tell front document to tell active sheet
set t to (first table whose selection range's class is range)
tell t
set tCell to (get selection range)'s cell 1's name
set colLtr to tCell's text item 1
repeat with c in cells
tell c
set f to formula
if f is not missing value then -- common cases first
set dRef to tCell is in f ¬
or "(" & colLtr is in f ¬
or colLtr & ")" is in f
if dRef is false then -- dependents via range refs
set rRef to false
repeat with i in my splitFormula(f)
if i contains ":" then -- we have a range
tell t to set theRange to range i
repeat with d in theRange's cells
if d's name is tCell then
set rRef to true
exit repeat
end if
if rRef then exit repeat
end repeat
if rRef then exit repeat
end if
end repeat
end if
if dRef or rRef then set background color to "red"
end if
end tell
end repeat
end tell
end tell
end tell
to splitFormula(f) -- lists components of a formula so ranges can be extracted
set text item delimiters to {",", "(", ")", ";"}
return f's text items
set text item delimiters to ""
end splitFormula