application defined or object-defined error with if statement

whenever i try to run this code i get that error on the if statement and i don't know why, please be advicsed that rcolor and info are defined and work perfectly i just chose not to put them here since they are quite long and won't affect the question in any way
and M8 is brought from a different sub

Sub Schedule(M8 As Variant)
If eTime = "900" Then
retry1:
                                    If IsEmpty(Cells(8, M8).Value) And IsEmpty(Cells(12, M8).Value) = True Then
                                    Sheets("Schedule").Cells(8, M8).Value = info
                                    Sheets("Schedule").Range(Cells(9, M8), Cells(12, M8)).Value = ","
                                    Sheets("Schedule").Range(Cells(8, M8), Cells(12, M8)).Interior.Color = rcolor
                                    Sheets("Schedule").Range(Cells(8, M8), Cells(12, M8)).BorderAround Weight:=xlMedium
                                    M8 = M8 + 1
                                    Else
                                    M8 = M8 + 1
                                    GoTo retry1
                                    End If

i've been stuck on this issue for quite a long time and would appreciate any help, thnx in advance.