Determine Which Text Box Has Focus

I am using excel VBA userform and have the following elements:

1) .textboxA
2) .textboxB
3) .commandbutton_insertdate

(clicking on this button will insert today's date into either textboxA or textbox B. I use an accelerator 'D' so user can use Alt+D to insert the date conveniently.)

My question is: How can I determine which text box (A or B) is in focus when i execute Alt+D?

My objectives are: When focus is on textboxA, and user Alt+D, today's date will be inserted into textboxA When focus is on textboxB, and user Alt+D, today's date will be inserted into textboxB

My problem is: It seems that when I use Alt+D, the focus will jump to the command button instead, so none of the text box are in focus!