Two workbooks and need text changed after comparing them

I'm hoping someone can help me because I'm really stumped.

1) I have two workbooks (sample1 & sample2). I need to be able to compare values in column A on both sheets.
2) IF a value in column A for sample1 matches a value in column A in sample2 I need column B values in sample2 to replace existing column B values in sample1
3) I have other data in columns C&D in both samples but those need to stay unchanged.

Could someone please help? This would make my day!!
Thank you!
~S