Dynamic sheet-reference in MATCH-function

I want to be able to change the sheet a MATCH-funtion points to by picking the sheet name from another cell. Is that possible? It doesn't have to be MATCH-function. It can be something else.

One example is a worksheet with all the months. I want to be able to change the month in cell A1, but want to keep the MATCH-function in cell B1. This function shall point to the sheet referred to in A1.