Plz Check :
https://docs.google.com/spreadsheet/ccc?key=0AlMNziTCmrQIdEhyQUJIODZoTTRMRVBWbk1LWHpMTWc
Hope this will help, if i get your problem correctly
if you use =isnumber(Cell number), then it VALID only for NUMBER [by default, it take the Boolean value as TRUE], so you validate the cell for only NUMBER by yourself. So why it VALID anything other than NUMBER?
Count the number of row of data area (naming as "mydata"): =ROWS(mydata) [assume @ A6]
Count the number of column of data area (naming as "mydata"): =COLUMNS(mydata)ll [assume @ B6]
To get the row and column number matrix:
for ROW:
Any cell (Say A8): 1
Next cell (A9)...