write a specific offset to an fat16 SD card file?

ok, so basically,

long offset = rowxColumn;
correct?

Since there is no situation presented by the op, I'll create one for the sake of furthering the example.
lets say we are dealing with a potentially very large user created word list that has the following intentions for using it
-A function to place the word in the file

  • A function to fetch a word based on the first letter proposed as an argument (then based on a concatenated second letter and so on up to about 4 letters)

The point of the offset being to search the file, reading as little redundant information as possible.
How would one approach creating the "long offset" during run time rather then pre-defining it?

for example the user gives the letters "at" and maybe the file was built by different combinations of letters row by row like so,
abs row 0-absent abstain ect...
at row 1- atone atmel ect...
att row 2-attach attainment attempt ect...

even though "at" only needs to be converted into the column value 1 it seems like seek() takes two arguments consolidated into one long. How would one go about creating "long offset=1x0" after deriving that column value equals lets say "int column=1" & "int row=0". I suppose its not as simple as just using "long( )"?