Access – Combination ID field

I have three tables, each creates it own set of ID numbers (through autonumber). therefore i have Table A, with ID’s 1-10, Table B, with ID’s 1-10, & Table C, with ID’s 1-10.

Once details have been filled into one of these tables, a Fourth table is opened. Within this 4th table, i want an ID field created automatically by Combining the id field (from the record you just filled) with thetables name, therefore if i had just created in Table B, a record with the ID 23, then the combind ID would be B23.

Hope this makes sense!!