(This is pretty weird, I answered this once already today, and yet I can't find my reply here, now.
I must have done something wrong, because this board couldn't be screwing up ... can it? ... Nah! )
Anyway, the answer to your question "can you use excel formulas in tables in word?" is YES.
In WORD, in a table that you have, you can select the command: Table>Formula
That will insert a field into that cell. Not all of the formulas you have in Excel can be used, but you will have no problem with addition (SUMs) or multiplications.
You could also use the Insert>Field: = (Formula)
When you first enter the formula (or field) the calculation will be done right then. The data will NOT automatically update again until you use a "Update Field" command. You can do that by clicking on the field (which will sort of gray the data there, and you right-click and select the Update Field command. Alternately you can also select the data (it will gray) and then press the <F9> key.
Probably the biggest problem is keeping track of the cell addresses, since the A,B,C etc is not shown across the top of the table, nor the 1,2,3 row number is not along the left.
Good luck, have fun.