Correct Syntax To Write Command Line Able To UPDATE More Than One Field In Table

what is the correct syntax to write a command line able to UPDATE more than one field in the table records having multiple WHERE criteria.

Here is my challenge:My TableI has the columns A, B, C and D which are populated, for example, as follows:

TableI
A B C D
1 2
2 6 4 3

1 7 5 9
1 2
2 5 8 5
etc.

I also have a FormII which updates TableII. Among the existing fields of TableII there are the fields C and D (same as above). When saving data entry thru the save button of the FormII, fields C and D will be naturally saved on the TableII. Well, I also want C and D info updated into Table I as well, but only when field A=1 and B=2.So what I need (for the click event of the button save in the FormII) is to open TableI and either insert or update it with the values of the fields C and D in every record WHERE A=1 AND B=2.For instance, assuming C=& and D=%, the desired result should be as follows:

TableI
A B C D
1 2 & %
2 6 4 3
1 7 5 9
1 2 & %
2 5 8 5

I did not find any examples in the net including multiple criteria..Here is what I wrote unsuccesfully:

Private Sub BtSalvarFrmII_Click()
CurrentDb.execute "UPDATE TableI"
Set FieldC = Forms!FrmII!FieldC.value AND Set FieldD = Forms!FrmII!FieldD.value WHERE FieldA = 1 AND FieldB = 2
Docmd.save
Docmd.close
End Sub

What would be the correct syntax?