i have table (x) that have primary

[TIPtip]

i have table (x) that have primary key from two fields(a,b).
When i insert values in another table into fields a1 and b1 and i choose from lookup table(x) field(a) from table x i want that automaticaly field b1 is filled with value b from table x.

how to do this?

Are thre any triggers?

 

[BNPMike]

You can't do this. If the key is a plus b then a does not determine b and no trigger can guess its value.

 

[TIPtip]

thank you