mdb & mshflexgrid

I have:
Txtposition
Txtnum
Adodc1
Mshflexgrid1
Problem:
I want to store text1 data to mdb where txtnum=!num
but I want to check whether it is already in mdb or not.
I show my mdb data in mshflexgrid.

Sorry if it is difficult to understand.
Tq,
VH