Yes you can call another event handler from another event. You just have to create necessary parameters.
However I suggest that you take the actual code to separate method so coding would be easier and much clearer. Something like:
void datagridview_Keypress(...) {
MyMethod(...);
}
void Datagridview_Celldoubleclick(...) {
SomeOtherMethod(...);
MyMethod(...);
}
void MyMethod(...) {
... actual code ...
}
void SomeOtherMethod(...) {
... actual code ...
}