Click on the cell that will contain the value from which you want to subtract minutes. Select "Format" from the Cells section and click "Format Cells" to open the cell format settings.

Press "Custom" and type the desired format for the cell in the Type box. Use "hh" for hours, "mm" for minutes, "ss" for seconds and "AM/PM" if you want to represent the clock time. For example, if the cell will hold a value such as "1:30 PM" you would type "h:mm AM/PM" (without quotes here and in subsequent commands). Alternatively, to display time units like "30 hours, 2 minutes and three seconds" you should use "hh:mm:ss" as the format.

Press "OK" to save your preferences and repeat the process for the second cell. As this cell will contain the amount of minutes you want to subtract from the first value, use the "hh:mm:ss" format.

Insert the time values in the two cells. For example, if you want to represent one hour and 30 minutes in the second cell, you should type "1:30:00."

Double-click a third cell, which will hold the result of the computation. Type "=cell1-cell2," where cell1 and cell2 are the first two cells. For example, if you used cell A1 to hold the first value and cell A2 for the second one, you would type "=A1-A2." Press Enter to display the result.