substract the values in dialgrid in vb.net

Question

hi every one,
i have done the project in the vb.net
in the i used dial grid for list out the values
in that the dial grid contains 3 columns and  15 rows
i have to substract the value from first row cell to second row cell
the result should be placed in the third row cell

for example,

5    3      2


regrds
vijay